Out of interest, what forum was this?

It's a simple phpBB board dedicated to fans of an old, no longer running TV series.

Do people regularly roleplay there?

Yes, in a very unstructured, somewhat silly, freeform sort of way (that evolved from the fanfiction section of the forum). There aren't rules, as such, but Deus Ex Machina and spotlight-hogging is frowned upon - using other people's characters in a scene is (oddly enough) fine, as long as they are portrayed in character. (And I use an AI character in those threads; before long, I was not the only one).