I once considered a system that simply coded the amount you're typing, whether it's emotes or talking or such, roleplay for the most part doesn't happen unless you're typing something, but I couldn't think of ways to prevent it being abused.
I still remember having an interesting RP exchange when Nathaniel and Kinai made a few trades etc, and being rewarded exp for that. I felt like a little girl on Christmas Eve. If text lines vs exp given doesn't work, then why not just "give a cookie" of exp as a GM every now and then? I feel there's so much good RP that goes unrewarded, and I don't mean just me. Sometimes I just sit at the pond of Hempstead in stealth mode and listen to each unique conversation that goes from discussing the day to sharing a life story and contemplating the meaning of life and good and evil.