Complicated version: Once you post a question to the community, the discussion belongs to the entire community, not just you. If you don't like the direction that the discussion is taking, too bad. It's not your choice where the discussion goes or when it ends.
I will ban people who delete their entries. And I will enjoy it, because it's one of my pet peeves.
This applies to comments as well. If you delete someone else's comment, with the exception of anonymous spam, you'll be banned. If someone is breaking the rules, contact a mod - or screen it, if absolutely necessary, and contact a mod. We need the evidence in order to ban the person or report them to LJ Abuse, if it's something truly serious. Don't delete your own comments because you regret them, either. If you made yourself look silly, suck it up.
(I know someone is going to ask about deleting & reposting right after a comment is made to make edits - so yes, that's fine, as long as you're not trying to cover up what you originally said. I can also see questions about deleting because you posted to the wrong community - yes, you can do that to, although if I didn't catch it while it was up I might ask you what happened.)
EDIT: And yes, if you delete your post, I will probably ask you what happened in the latest post of your journal - because that's the most sure way that's left to contact you, with your post gone. If you don't like it, don't delete.
If you're bitchy to me about bringing comm business into your journal after you delete a post, I'll ban you because you're being a stupid asshat, especially if you ban me because you can't handle being told not to break the rules again, omgwtfisyourproblem.