It took Harry a week to perfect a way to isolate himself from Hogwarts ambient magic that was both sustainable and unnoticeable unless looked for. Just flaring his magic out like an Aura did the trick but would have everyone staring at him in awe and disbelief as his presence pressured them. In the end, he incorporated the idea of the Bubblehead Charm, his Aura, and the Shield and Disillusionment Charm into one spell.
The Bubblehead Charm gave him a constant supply of uncontaminated oxygen.
The slight use of his Aura protected him from influence just enough to not affect those nearby.
The Sheild Charm tied it all together and solidified it around his entire body.
The Disillusionment Charm targeted the shield making it invisible.
It was complicated to combine all the parts, but once he did and memorised how it felt and acted, it was then a simple matter of using his considerable willpower to enact the final product whenever he chose. The hard part came when he had to train himself to subconsciously keep it active.
In the end, even with his mental prowess, it was much easier to make it last for an hour when it was cast and then just reapply it when it timed out. Harry would have to shield his bed for when he slept, but that was still much easier than training himself to keep spells active while sleeping. Not to mention that isolating a stationary target from outside interference was child's play compared to adapting it into a charm to cover a moving human target.
The week it took to implement his new protections had kept him paranoid of all his decisions and actions, making him triple check all of his choices before acting. After they were in place, he went over all of his actions after he had entered Hogwarts and evaluated them objectively. He did not like what he observed.
He acted like a child on a sugar high and was not subtle at all about it. He had blatantly defied the Dark Lord in front of everyone and then did the same to Snape, purely because his own ego would not allow himself to look weak! Fair enough he got away with it, and it was satisfying to give them a nice hard metaphorical slap to their faces. Still, the consequences were gaining everybody's attention and alerting the Dark Lord to his real personality.
There were no significant changes to personality or anything, but all of those out of character choices happened the first week he entered Hogwarts! Hell, it was in the first hour that he felt the need to throw down with the Dark Lord! Imagine what he would be like after seven years of Hogwarts eroding his reason and inhibitions! He would probably start acting like Hitler and attacking everyone at once because he was sure of his superiority!
Luckily he caught the problem early. Even though he had made a few slight mistakes that now had Dumbledore watching him closely, Harry had already accounted for this situation before coming to Hogwarts anyway. It was the seat of the Dark Lord's power after all! He would just need to keep his head down for the next couple of weeks for everything to quiet down. Then, when everyone fell into the monotony of school, he could start to explore the magical castle.
Because Harry was in Ravenclaw, he did not have to deal with the flying class drama that ended with both Draco and Ron having a months detention after destroying Nevile's Remembrall and disobeying orders not to fly. With Harry's new perspective into wizard stupidity, so many things made sense now. Like why a rich Pureblood would risk the stigma of being labelled a thief, or why a shy, abused orphan would suddenly jump into the limelight to return a strangers property at the risk of his own life.
Harry decided to let Ron and Draco develop their feud so they would be too busy to concentrate on him. Ron had tried a few times to insert himself into Harry's influence and claim friendship while snubbing everyone near him. While Draco remained professional and invited him to play with his group of minions. Both cared little for school and had their sights set on childish pursuits because, well, they were children!
But while Draco understood Harry's need to learn about his heritage, his go-to excuse for turning Draco down politely, Ron took it as a slight. He became belligerent when he was continuously rejected in favour of studying in the library over playing a game of chess. Soon he and his half-blood cronies Seamus Finnigan and Dean Thomas could be heard slandering Harry about being a stuck up Pureblood.
This did not really bother Harry, but he soon became aware of different looks from the half-bloods and muggle-born of the different years and didn't want the sheep to start developing a negative impression of him. So with only the slightest bit of reluctance, as he hated Ron Weasley in the books for being a complete and utter wanker, Harry made his way over to the Gryffindor table at breakfast under the watchful gaze of the entire school.
Dean and Seamus became nervous as they noticed the entire school looking at them and then paled when they heard Harry clear his throat and turned to see him standing behind them. Ron continued to shovel food into his mouth like he hadn't eaten for a week, his eating utensils discarded in favour of his hands.
Ron failed to get the 'subtle' hints that someone was behind him wanting to talk, so Harry just came out and addressed the red-headed pig directly.
"Ron Weasley, I hear you and your friends have been slandering me by saying I am a Pureblood extremist that hates muggle-borns. May I please know how you came to such a conclusion so that I could clear up any misunderstanding?" Harry said loudly and clearly, so the now silent dining hall had no problems hearing his every word.
Ron was so startled from his single-minded devotion to eating that he jumped when Harry called out from behind him. The whole school was treated to the lovely sight of half-chewed waffles falling from his open mouth onto the table beside his plate. The jealous little sh*t immediately turned bright red when he noticed the disgusted looks from everyone, and this only made him more prone to lash out at the cause of his embarrassment.
"What do you want, Potter? Don't you have some books to read with your rich friends?" Ron spat out with a few additional bits of waffle. Being so startled, he had not heard what Harry had said after saying his name.
"I was merely wondering why you, Dean and Seamus have been slandering me. The rumours that I have overheard say that I hate anyone that is not a Pureblood Noble and especially despise muggle-borns. I was curious how this misunderstanding came about and have since traced it back to you. Also, could you please swallow your food before you speak?" Harry calmly replied.
"What's the matter? Not good enough for your Pureblood traditions?" Ron replied smugly, once again missing the question and latching onto something he could use as an insult.
For Harry's part, he just looked at Ron like he was an idiot. He continuously kept forgetting he was dealing with children thanks to his foreknowledge of seven years familiarity of everyone's character.
"You do realise that if you are going to bring up blood status, that you are a Pureblood while I am a Half-blood, right? But manners have nothing to do with blood status, even muggles would find your manners lacking."
Ron reddened further at the rebuff and continued to blurt out nonsensical insults like the uneducated and isolated eleven-year-old child he was. He would have been much better at this if he had more contact with children other than his brothers. As the youngest child, Ron was always on the receiving end and had no experience dishing it out. Even Ginny regularly put him in his place.
This was why Draco verbally slaughtered him at every turn. He was explicitly trained by his father how to talk and act like a Noble, as it was expected of him to be better than his peers.
"Yeah, so what? I'm a Weasley, we don't care about stuff like that! Now, how about you shove off, slug breath!"
Percy had gone pale at the damage just done to the Weasley reputation and further cringed when he noticed his crush Penelope Clearwater looking at him funny. Fred and George just took it in their stride but were still in disbelief about their youngest brother's vendetta against the boy-who-lived, it seems that even Potter didn't know why Ron was angry at him.
"Yes, well, I would be happy to leave after you explain why you are spreading ridiculous rumours about me." Harry soldiered on, wanting Ron to put his foot in his mouth before his brothers could defuse the situation.
"What's there to explain? You always look down on everybody that isn't a Pureblood. Spending all of your time in the library instead of hanging out with us! We not good enough for you, is that it, Potter?" Ron happily obliged in destroying any credibility to the lies he spread.
Making the best put upon face while he sighed, Harry lanched into a cutting rant that should keep this idiot away from him for good. If not, he could always supply Draco with ideas to keep him busy.
"First of all, once again, you are a Pureblood while I am a Half-blood. If anyone was discriminating, then it would be you for slandering me, a Half-blood, for no reason other than I wanted to study in the library instead of playing chess with you!
Second, I have just found out that I am a wizard, and so were my parents. After they were horribly murdered and I was then abducted, ten years had passed before I even knew their names or what they looked like! Forgive me for being so selfish that I wanted to find out all I could uncover about them and my newfound heritage!
And as far as me hating half-bloods and muggle-borns? I can not believe you can be that stupid, simply because if you were, you would have died long ago for forgetting to breathe! The only person I can honestly say I dislike would be you, a Pureblood! By your logic, I now hate all Purebloods!
Nevermind that my father was a Pureblood, my mother was a Muggle-born, and that I am a Half-blood, I must hate one of those groups of people simply because you say I do! Please do everyone a favour and keep your mouth closed, especially when you are eating, you disgusting bigotted pig!"
With his rant finished, he spun around and calmly walked from the hall, his robes flaring around him thanks to Snape's spell gleaned from his mind. While not the best performance, it was certainly good enough for his supposed age and would hopefully put any blood supremacy rumours concerning him to bed.
Now he just had to wait for this bout of excitement and popularity to die down so he could start doing something productive...