aight let's see:
blocking some dude from seeing your post is a big no. not in this kind of forum, since it might cause inconvenience to innocent people.
blocking some dude from starting a thread is.. what the heck? i guess it should be mod's privilege, not user's.
blocking some dude from seeing your profile is something i might support, since one's profile hints one's identity.
and some dude that is blocked shouldn't supposed to be able to send DM to the blockee, i mean what the heck thats creepy