> Is it that if you write enough buggy code you get banned as a contributor?

If this is a consistent issue, your contribution would (ideally) be continuously put into a backlog until someone else with no connection to you verifies that it's as bug-free as it appears to be. (Excluding non-obvious security & performance issues)

> Is it that you're not allowed to say Claude ate my homework?

Yes. As the contributor, you should be the first one to look over the code, not someone else.