Perhaps the issue is that formal writing requires a kind of discipline which RP side steps as a form of recreation. But then, no, that would suggest that acting doesn't have its own discipline which (while social) can be no less rigorous. Hmm. Not sure.

I can't boil this down to different modes of expression. I mean they are, but these are differences of kind, not of degree. They are fundamentally different enterprises. On that I'll not budge.

As for the solitary thing, I believe it's necessary. I know that to others it's not. But I still maintain that roleplayers who claim they're partaking in "collaborative writing," or any sort of genuine writing, are either mistaken or deluded.

Typing, even acting via typing, isn't writing.