Pythagoras: Sorry Pythagoras, but I think you are not totally right. E.g. because of the cannons it's an everyday's situation to answer a check with a check. The situation mangue mentioned is a draw, as both players violate the rules and it doesn't matter which player began:
Another thing: At IYT they programmed, that its forbidden to check more than three times by moving the same piece, which is complete nonse, because you often need to give some hidden checks (with cannon and horse eg.), where you take several opponents pieces with every hidden check. So the important point is, if there is a notable progress in the position or not...
If I find the time this evening I will write down the repetition rules as far as I know them.