I would love to agree with this, but...

Some people actually feel that if your character hates their character, you are actually hating them. So by telling them that they need to check their eyeballs, that could be seen as passively telling the other player that they aren't being observant. This stirs up the OOC drama that you were trying to avoid. That's not to say this method doesn't work, but you need to be careful with the wording, and who you use it on.

I feel that mildly misses the point. I guess it depends on how your actual character is (personality wise) in the roleplay. You don't have to say something offensive, if your character is kind. The character can say. "Um, excuse me but this isn't chicken, it's actually lettuce." My main point, is going with the flow and not whining about things you don't need to. You should be able to role-play well. Which yes, does mean read everyone's stuff. But don't use player knowledge as character knowledge. And don't have a stroke if someone seemed to miss something you've wrote. Because it may be laziness, or it may be a genuine mistake. But almost every OOC fight I've ever had or seen is because someone wasn't smart enough to just roleplay out of a situation...(and nearly every situation was something that could be solved.)

If anyone has gotten actually offended (not their character) but the player themselves, at a brash/offensive character acting that way in a roleplay they're flat out not meant to do this...