a mod should really answer that, Mauser, but there is no particular point in deleting your thread(s), unless you have said something embarrassing or stupid
(you know, something like I might do !)
if you do delete it, I believe it is gone gone forever, not saved in the database
shucks there are LOTs of ancient threads here, folks sometimes do find them useful, leastways if they bother to use the search function
I do not think you can actually delete threads though, only your own posts, unless you are a mod