I think it is very important to differentiate resigning from quitting (just disconnecting, doing nothing for minutes...). The latter (if it does happen on purpose) is not acceptable and I would blacklist any player who does behave that way. Resigning is a valid option. It is an option the interface offers (just like buying cards). It is a move within the context of the game. It is IMO neither impolite to buy a torturer nor to click resign. Hitting the resign button communicates: "I am convinced that I am no longer able to win this game (whatever the reasons may be: worse deck, inability to get enough victory point, boss calling). I congratulate you to your victory". I don't need to express this in the chat. The intent is clear. (The intent of buying a torturer is also clear: "I want to torture you ;-)").
My opinion is: it is absolutely ok to resign anytime - some might prefer to explain themselves, but I do not expect them to do this.
My opinion is: it is absolutely ok to resign anytime - some might prefer to explain themselves, but I do not expect them to do this.