It's extremely rare for a thread to actually be deleted in the JK.net forums. It's usually locked, plus getting an edit if needed. I'd tend to think of mainly server problems for such an incident. About getting rid of deletion - I like having the option to delete my posts. I've used it to eliminate things I said that were redundant, irrelevant, etc. in the past. Not letting people delete posts just doesn't seem to have any real positive effects.
"Words are deeds." - Wittgenstein