Sav
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I've seen screenshots of the chat, and the gray color indicates that the player was correctly identified. This isn't the only time you've left a game recently. And the insults directed at the administration only worsen the situation; you are taking on the role of the cheater here.
Suspecting someone of cheating doesn't give you the right to leave the game. You should finish the game, surrender, request a password, and report the player. If you can't prove it, just add them to your blacklist and don't play with them.