I see several ways people post. If you find a super good deal, you might post that dollar amount. Otherwise, leave it open to chat with the person, he/she may already have a preference.
Before you ask, if you find a roomshare, you book and give private info to one travel agent, that agent will link the booking together.
I don't know how successful this site is, sometimes you see no follow through on the site, but maybe the final steps are done on a more personal level.
P.S. I answered your e mail.