playBunny: The 100 points was what A and B agreed the game was worth ... if they had agreed 200 points then the 3 results would have been:
A wins - A goes to 2050, B goes to 1450.
Draw - A goes to 1950, B goes to 1550.
B wins - A goes to 1850, B goes to 1650.

The purpose is to make it worthwhile for the better rated player to actually play the game. I have games now (particularly in Tank Battle) where I will either stay the same (if I win) or go down if I draw or lose. Hardly an incentive to play as there will always be a game or two you will draw or make a silly mistake and draw. As you say, possibly not sufficiently independant to be a rating system.

AbigailII: I understand what you are saying about being unratable without a draw or loss (likewise someone who only ever losses is also unratable) ... no doubt it is to do with trying to divide by zero. But it is not that they exceed the rating system, it is that they are outside it! Maybe they should not be even given a provisional BKR until they do have a contrary result or have reached the stage where they have completed 25 games and can get an established rating. I know of only one or two players here who are so exceptional in their particular game types that their would warrant such a high rating from scratch.

So here is another suggestion ... A player's rating may never be more than say 10% higher than the highest player they have beaten or equal with the highest player they have drawn with. This would encourage them to play the higher rated players and they would not be able to obtain unmerited BKR levels by playing moderate players.

WQ:)