Posting a "critique" in the OOC is definitely a surefire way to cause drama, if not make someone abandon the RP entirely. I witnessed someone telling someone to "use the enter key," and 3 other players plus the GM parroted this advice back to them. Needless to say, they left the RP they were in. Shortly afterwards, I noticed other players started to become self conscious of their writing to the point where they left, or found fault with the GM's lofty writing expectations. Nobody wants to endure public humiliation.

	My boss's motto about employees is that you never want to let them know you are dissatisfied with them. And I think a GM should behave the same way with his fellow players. I'm very fortunate in that the RP I run is filled with writers who meet or exceed my criteria. Telling people how to improve their writing is not something I feel comfortable with doing. It would be one thing if I was on friendly terms with them. But some of these people I don't know especially well, and I'd hate to drive them away on account of them parroting other posts too much. 

	If a player or players have a problem with a particular user's writing, they should talk to the GM about it. And if the GM feels it is necessary, they can address it. Sometimes I know I should do something, but don't because I think I'm alone in the decision. 

	And ditto to what Pugbutter and Odin said. there are far too many assholes and people with sensitive feelings to allow everyone to openly critique. This is something that, when it needs to be addressed, should be done via PM by a GM.