It's been a long time since I had implemented this on Tyme but if I remember correctly this is how it went:
Players had a flag to signify if they were IC or OOC. If you were flagged IC you couldn't claim your character wasn't in a room - this was so catching spies was feasible as there were ways to be invisible. If you were flagged OOC you could still explore the grid, go anywhere you liked, etc but you couldn't see other people's poses.
Players had a flag to signify they were looking for RP. It'd revert to off after a period of time and after certain events to help avoid false positives.
The +where command (well, its equivalent) showed you no names. It only showed you how many people flagged IC were in each room. If any of them was flagged as looking for RP you could also teleport there directly without need to go through the +meetme/+agree handshake, otherwise of course you could be summoned over.
It was an easy system so it saw good use.
I never found RP channels to be worth much since they're spammy when you don't want them and pretty serendipitous when you do - since everyone must be looking at the same time to see it.