Re: Change a topic into self-moderated retrospectively / add polls retrospectively
Sorry 1miau, I agree with @hosseinimr93 here: if one posts into a self-mod topic he knows that his post may get removed. This doesn't happen with a "free" topic. Changing this "during the game" is unfair advantage for topic owner.
Once in a while, a user goes wild and deletes all his own posts. It would be much worse if he can delete all posts in his own topics too.Quote
Previous comments shouldn't be affected. 
This would make sense, but may be more difficult to implement.