Posts [b][i]can[/i][/b] be removed/deleted, but it won't impact the post-counter of the thread.

Example, if you accidentally post an OOC post in the Char Tab when there's 11 posts in it, you'll bump it up to 12. If you then ask a Mod to delete said post, they can - but the Char Tab will still say there're 12 posts.

My own RP is a good example of that, because that very example happened to it. xD