As the creator of a thread in the Play by Post forums (ie: the DM), it would be nice to have administrator privileges to be able to edit other player's posts. I would personally like to be able to go into their posts and slap stuff in spoiler tags just to clean things up and maybe strike-through portions of their actions that can't happen for reasons (with an explanation, of course).
As a player, it would be nice to have signatures specific to threads. I could put my character's vital information like AC, Health, spell slots, limited use skills, etc... and have several of these signatures for several characters across multiple campaigns.
I don't know if this is possible, but: