The forum rec.games.frp.advocacy is a Usenet newsgroup for discussing comparisons between different role-playing games (RPGs) and RPG styles. It was started in May 1992 as an offshoot of the group rec.games.frp.misc. The original intent was for it to be a place for heated arguments ("flame wars") between advocates of different games. However, in the process of hashing out differences, a set of contributors began to actually discuss core concepts of role-playing: what it is, how it works, what styles and techniques exist, how to do it better.
I believe that the key development of the group was an acknowledgement that there are different valid styles of role-playing. Different role-playing games are not merely different methods to achieve the same goals, but actually different goals in themselves. It pushed past differences to allow at least some discussion between gamers of very different styles of play.
To go over a bit of additional history. Early debate was over specific systems (such as GURPS vs Hero). There was some effort to generalize: debating the merits of universal vs setting-specific systems, and the role of game balance. In May 1994, David Berkman joined the group, championing the cause of diceless role-playing and in particular the Theatrix RPG which he editted. This widened the scope of the debate considerably. In August 1996, I wrote the first version of my FAQ. Between May and August 1997, the idea arose of a "threefold" model of games: dividing them up into Dramatism, Simulationism, and Gamism. In August 1997 around a dozen of the posters came together for the "RGFA Gathering" in Alberta, Canada.