vBulletin has the option of allowing users to delete their own posts... I think this should be enabled. This would most likely be a soft-delete, so the mods could still see the deleted posts if desired, but would allow users to patrol their own posts when needed (e.g. forum glitch causing a double post; mistaken post in the wrong forum; user decided their post was out of line; etc.).

Especially lately, I've seen a lot of posts that say "deleted - duplicate" because the website glitched, but users have no way of deleting their own posts.

This is a fairly minor feature that really has no downside to enabling - users can't delete anything but their own posts, but it would allow users to help do some of the maintenance on their own, taking a bit of load off the mods.

There's really no reason NOT to enable this...