El Cid: The problem is the rules are whole texts. It's hard work to write the same stuff over and over again for the over a dozen chess variations (I know there's copy paste but you still have to go in and find the differences to change). And then, if someone says "Oh look, you made a mistake there" you must go through all the texts to see if the mistake is in the others or not.

A suggestion for Fencer - why not have the rules broken down in small bits that can be used to compose the actual rules page. For chess, for instance, you could have a text saying how the pawns move, let's call this text 1. Text 2 saying how the king moves etc. Then, text 30 says how the game is won after 3 checks. Then text 31 that the game starts with random positions.
Rules for 3 Checks Chess would be composed of 1+2+...+30;
Rules for Capablanca Chess would be composed of 1+2+...+31.

Of course, I know this is easier said than done. But in the long run, it could also make the complete rules easier to maintain and translations easier to do (it takes lots of motivation to go and translate big texts like the present rules).

And in an ideal way, you could even link this texts to bits of code in the game engines and so the rules would come out automatically :) (yes, I know, I'm daydreaming now)