I'm always Out of Character unless I'm posting in a Role-play, because it confuses people to say you're "In Character" in an Out of Character discussion thread.
My biggest problem with it is that some people harass new members with stuff like "I WILL DESTROY YOU" or whatever because their character is a Sith, and then act surprised when the new person didn't know they were "In Character". Always assume people around you think you are posting Out of Character, as it's inconvenient and confusing for others.
Out of Character forums are for Out of Character posting, In Character forums are for posting In Character. If you're posting OOC in an IC thread, you'd mark it with the words "OOC", show the same courtesy in OOC threads.