So first of all, we use a standard ELO rating system here on the site. Here are the answers to your questions:
- We use the following multipliers for board sizes: 19x19 (x1.0) 13x13 (x0.5) 9x9 (x0.25)
- Only the result will affect your rating
- adjusted by rating… rank is just symbolic
- It’s just determined by the rating, see (1)
- In the standard elo system that we use, ranks are 100 rating points wide… that bar represents your progress from one rank to another given your rating (though it gets weird if you are below 30k because 30k is the lowest we represent you)
- See (1) for our calculation algorithm. It’s a pretty basic system… the reason we use it is because it is easy for players to calculate what change to expect. Actually… you will lose more points for losing to a lower ranked player than an even ranked players. Also… you will lose fewer points losing to a higher ranked player (but you would gain more for beating them)… up to a certain point if you lose to a much higher ranked player you will not actually lose any points (likewise if you win against a much lower ranked player then you will not gain any points)
Unfortunately we are just two guys… we are a little slack on our documentation, but it’s not because we want to hide anything we just haven’t gotten around to it yet. We have been working on a very large update and more documentation is on the roadmap after the next release.
(1) http://en.wikipedia.org/wiki/Go_ranks_and_ratings#Elo-like_rating_systems_as_used_in_Go