nabla: Measuring activity is not easy to do. A Glicko system is better than an ELO system, but both Glicko and ELO assume matches are almost "instantaneous". That's not true for BK. Someone can be quite active (that is, making lots and lots of moves), but lose "activity" (increasing the RD value in Glicko, or disappearing from the rating lists in the current system) because his games are finished yet. In theory, it's even possible for someone finishing just 2 games a year to remain in the rating list, while someone who plays 500 of them each year disappears for months, just because all his games finish in November.

Having said that, Glicko would be an improvement over the current rating system. Its activity measure isn't perfect for a site like BK, but much better than we have now. And any rating system worth its salt should not consider a match won 6-4 to be equivalent to a match won 10-0. (In proper ELO, someone winning a 10 game match 6-4 may lose rating points (the rating difference gives an expectation of what the final score of a match should be; if you do better, you win points, if you do worse, you lose, regardless of the final score)).