If the offending element is one's personality or one's beliefs, then yes, one can come back by removing that, but it's the same thing as not coming back.
Not really: we see on Reddit all the time how subreddits quickly descend into herds that can only upvote accepted ideas and instantly downvote to oblivion or ban anything even neutral (much less antagonistic to the subreddit’s worldview).
Anybody who comes by with a different take immediately loses interest in the group and so there’s a self-perpetuating system that makes the group more and more fanatical about right-think and wrong-think.
On Twitter, deleting tweets for wrong-think has largely the same chilling effect and self-perpetuating descent into an echo chamber.
Never because you own it and have rights just like the Supreme Court has established that most private businesses has the right to kick people out. If people don't like that then they should petition the government to take over Twitter and make it a utility or government service.
"No offensive t-shirts" is not the same thing as being banned lol