When is Flagging Ethical?

Ok, well my point of view on it is this is something I prepare for all game long. In other words let's say it's move 20 and I'm ahead on the board, but 1 minute behind, that's something I'm going to notice, and if it's a 3|0 game then I might consider the position equal, and so I'll speed up in a way that's willing to sacrifice some position for regaining that time on the clock.
Similarly when choosing which endgames to go into, I consider how long they'll take to win. If it's similar to your game and I have a good position on the board with 1 minute vs my opponent's 3 minutes in a difficult endgame that will take 40 moves (and my opponent can make threats so I have to be careful), I might evaluate the position as lost for me... that means when I'm flagged I'm not upset because I was expecting it.
The only time I get annoyed is in positions like this where both players have roughly the same amount of time (let's say both have 10 seconds)
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I think good etiquette is to willfully allow a rook trade, or allow a 3 fold repetition... some people go for a win, which I personally find childish, but oh well, on to the next game.


Flagging is always acceptable. Just like taking a piece or delivering checkmate is always acceptable.

There is nothing unethical to using the clock as another weapon in the game. However, at the opposite end of this problem, I tried to resign a speed game and couldn't find the gizmo to click on in the new reformatted chess.com.

Mr. Fischer said, you have to give up a square to get a square. And one of those squares in speed chess is the clock.
Your opponent thought for 90 seconds less than you did, but obtained more time for that handicap. Then he used is additional seconds to beat you. That is fair in speed chess.
The only real time playing for the flag is unethical is classically timed chess, and that shouldn't happen anyways.