This is an example of how a "discussion thread" for forum RPs could go to make the best use (that I know of). First: a full, solid description of the setting.
Every world has them. Meeting places for casual gatherings. Center pieces for towns and villages in the middle of nowhere. Somewhere to get drunk, kill time, and talk to complete strangers. Where information, people, and rumors mingle. It shouldn't be surprising, then, that the many universes and dimensions have one to share. Outside of normal time and space, or abnormal time and space for that matter, this tavern sits. Mid-evil knights trade stories with mages from other worlds. Werewolves drink with space marines. All sit and chat equal, because they are all just visiting. Echos of the truth that will disappear when the dreamer wakes...
Straight-forward and simple. A story fragment or plothook would come next, but in this case... there is none. This example is for an area for people to practice RPing their characters outside of the continuity of the RP itself. For rookies to build the skills, and for everyone to iron out personalities.
And from here, it's discussion. Questions? Concerns? Interest in what was presented? That part belongs to the rest of you. Tell the poster what you think!