I wonder what the statue of limitations is for pursuing something like this. I worked at a hotel that was being sued by another famous hotel because part of their name was in ours. We spelled it differently but we had been using the name for like over 20 years. Anyway it was thrown out of court because of the time factor. So I wonder if the MPAA can pursue this considering how long it looks like fan fiction sites have been using the rating system. If something is used long enough without challenge it can become public domain. I have heard of that as a case with land - letting people cut through. So it might be that if this can be documented as going on long enough and the MPAA has never challenged that they no longer can.
