Well, I'm personally pretty comfortable with using discord for RP OOCs. It's convenient to use in my cellphone and quite dynamic when compared to forum threads (and it also makes the thread less... Polluted, may I say). 
That being said, I kind of understand [@Raineh Daze]'s and [@Rin]'s complaints about it, as it is, after all, a private message app that some people use for real life stuff that they don't want to mix with role-playing. Even if not related to personal life, it's kinda hard to feel comfortable talking with strangers in a message app when you've just started to do so. Even i was like that in the beginning, tons of comic occasions ago.