
As far my own roleplay is concerned, if I'm roleplaying in /say then I'm inviting random people to join or at least attempt to join unannounced. There's really no point in roleplaying openly if you're not willing to at least entertain the thought of people from the world joining in.
If I don't want people to join, then I just go to party chat where I type in my usual third-person style.
If I don't want people to join, then I just go to party chat where I type in my usual third-person style.