Well as for deleting forum posts, the reason is because if posts get deleted either at the beginning or middle of a thread it can for the most part cause the thread not to make much sense. And in the past unfortunately we had members that would post personal attacks in a thread then go back and delete them after some time had past so people were able to see the attacks and start responding then the thread would get derailed.

Hope this helps explain some reasons behind this change.

Thanks