My favorite example of this is that Popehat (Ken White) was banned from /r/legaladvice.
/r/legaladvice is heavily moderated to keep it clean and high quality.
Ken White was banned for deliberate persistent rule breaking and hijacking the sub to make it popehatLegalAdvice.
https://amp.reddit.com/r/OutOfTheLoop/comments/7xpggl/what_i...
While /r/legaladvice is heavily moderated, it is not particularly high quality.