Actually, I'd prefer to be able to delete any and all of my posts as I see fit. If that's enabled then anyone responding to a thread would do so with foreknowledge that the thread could be deleted by the OP - everyone gets a choice to post or not. In any event, if the 'mod backup' you have proposed goes through then the thread wouldn't be completely lost; if someone was upset enough about the loss of their post(s) they could always whine about it to the mods/admin. It really annoyed me when they introduced that in cprog just because some brat was annoyed that his/her/its prize postcount was diminished because a thread starter chose to exercise their freedom of expression by killing what they created.
Still, since there seems to be a difference of opinion over this I suppose we'll just have to vote on it.