I mean, the fact that a subreddit based on making fun of people with disabilities even existed says a lot about reddit, just like dozens of other deplorable subreddits. Unfortunately some of those subs are still around to this day.
I’m sorry you went through this, the internet can be awful. The stuff I used to see on 4chan back in 2005+ was insane. In a lot of ways it hasn’t really gotten any better on reddit.
It’s alarming that when they rejected you, you doubled down and tried to adhere to their standards to fit in even more. But you were young and toxic groups like those exploit people all the time.
I hope now you understand it is not okay to make fun of disabled people like that.