PG wrote about this here: https://news.ycombinator.com/item?id=6813226.

No one here is likely to hold a grudge. I see you got hammered on one thread, but once you figure out what specific things to avoid then people will treat you appropriately.

I have had a few comments downvoted. Some of them a lot, but I learned that sarcasm doesn't translate well in text. Complaints about downvotes get downvoted every time, usually even by people who didn't mind the first comment.

If you are worried about your karma level then try to post interesting stories you find elsewhere. A comment will never get more than a few upvotes, but you can get hundreds from posting a story.

I don't think you can. You can scrub your profile of identifiable information, change your password to something random and then forget it, though.

Unrelated to your question, why are you leaving?