Even if they did, there is no guarantee that they would enforce the rules we came up with.
Moderating a forum like this is/would be a full-time job. There ARE forum moderators that sneak around and enforce ToS violations and the like. I know for a fact that certain members of the community have been looked at or banned for behavior that violates the ToS of the forums.
However, moderating RP based on guidelines set by the community is something outside Riot's direct scope, thus, it's unlikely they would want to expend manpower to moderate something based upon that. This means, effectively, that in order to have some semblance of order, we would first have to create the rules and regulations of the forum, which would be a tremendous undertaking in and of itself and cause a lot of in-fighting, then, we would have to have a way to contact Reds/Forum Moderators to inform them of someone breaking rules we have set in place, as long as they coincide with the forum ToS.
Such things could be trolling, intentionally causing disruptions, flaming, overtly sexual or graphic descriptions of mature acts, etc.
I'm not saying creating a list of guidelines and rules couldn't be done. Hell, I'd thought about doing it myself several times, but the thing stopping most individuals of taking that step is the inability for us to enforce any rules we may decide upon as a community, except, perhaps, to downvote the offending party into oblivion, which really doesn't solve anything.