"So you are saying if opponent disconnects and you press a button then the match won't be rated."
Yes, exactly
"What if someone is losing? He will be happy to press that button and avoid being rated."
I still have the option to have the game rated and would have no qualms in doing so if it was a clear case. I would probably give someone the benefit of the doubt once, but would employ the "fool me once..." rule.
"Surely, the one who DC'd and was in a sure win situation will be mad."
You make a good point about this. If the DC'd is so far ahead that the disconnect calc leaves him as the winner, I elect to give him the points but I recognize that not everyone would do so. It still comes down to sportsmanship. I guess you could just have the algorithm do the score calc and if the DC'd is still the winner, despite the default end(s) scores for the remaining player, the button would not be an option. The only unsportsmanlike play this would allow would be to habitually build up a big enough lead and then leave. Generally, only good players could do that, and it has been my experience that the better players here (with the odd exception) tend to play with the general sportsmanlike spirit of the game.
"you are behind but due to the DC you'd win. You press the button, fine. You don't press it (it's not obligatory or you think you'd have won anyway), then your opponent will accuse you being unsportsmanlike."
This case is somewhat moot. As it currently stands, the DC'd loses anyway. They don't lose any worse if I elect to push the button. I would lose, however, in terms of reputation if I chose to act unsportsmanlike.
Effectively, this is analogous to throwing the ball back to the team that kicked it out of bounds when a man is down.
One other thing this would allow for is to end a match prematurely upon mutual agreement.
While we're in that vein, it would also be nice to allow an opponent to re-take one of those shots that is taken when one accidentally clicks the mouse when lining up the broom and the rock goes about 10 feet.
Oh, and continuing in the vein of curling sportmanship tradition, if you could please find a way to have the winner provide the loser with drinks, that would be appreciated...on second thought, maybe not...my liver couldn't take it...
Thanks for listening.