The thing with roleplay is that it's an interactive story. IGS is really nothing more than an IC chat, where you chat in character, apparently. Although this isn't expressly written by anyone, and there's little rules regarding it - in fact the forum description says "roleplay" and "in character". To me, as someone who has roleplayed in this manner for over a decade, this involves describing your character's thoughts, feelings, motivations, as well as their actions and dialogue. What's considered IC and OOC on the IGS is indeed weird. Posting what your character is thinking/doing in their captain's quarters while conversing with other capsuleers is somehow "OOC".
Posting on the IGS is inviting character interaction. Posting on EVE Fiction invites player discussion.
If you go into IGS trying to interactive story - like you would in every. other. roleplay/IC. forum. ever. - you're gonna have a bad time, as I learned the hard way. It was actually rather insulting, after I spent all this work designing my character in the client, creating a unique backstory for her, a set of motivations and character flaws to explore, and then posted what my character was doing, thinking, and the message (scientific article) she opened for discussion with other characters - to have it moved to "fiction" and told that I wasn't roleplaying my character... it's like they were saying "everything you wrote is fake and invalid and doesn't actually exist." And then to be told that I wasn't actually roleplaying, and to read some IGS threads with their half-trolly antagonism and not-quite-complete-paragraphs, was really grating. Thus, my slightly less-than-polite posts to users who responded to my thread.
Elitism, a "cool kids" clique, the idea of "the right way" and "the wrong way", and resistance to change are prevalent in any RP culture. Without the mods stepping in and policing it with a clear concept of what RP, or at least what EVE RP is, the culture will remain as it is and stubbornly resistant to change and improvement.
I'm not suggesting that it should or does need to be changed. But it would be interesting, after all, to start a play-by-post, traditional RP, and get some quick replies/interactions with other characters in the same fashion, and see if CCP moves it or locks it.