This has long been a point of debate. I have a personal story to share, but first the two arguments:
*Argument 1: Exploit the mistake.* Every chess player has three resources--material, position, and time--and it's up to the player to use those resources better than his opponent if he expects to win. Managing your chess clock is a basic aspect of managing your time.
*Argument 2: Help the player out.* The clock is a tool that is subordinate to what's happening on the board and both players should use the clock to help them have a good game. It's in the interest of good chess to point out the opponent's error regarding the clock and it's in accordance with The Golden Rule: "Do unto others as you'd have them do unto you."
In one of my first OTB tournaments, my opponent didn't hit his clock after moving. He was a guy in his late 20's, I'd say, and was probably as inexperienced in tournament play as I was. I considered the situation for a moment and decided to use the time ticking away on his clock to analyze the board. I said nothing, but just focused intently on the board. This went on for two minutes... three minutes... five minutes. After ten minutes, my opponent was getting agitated and it was clear he was wondering what was going on: Why wasn't I moving?! Not long after that, he noticed his clock was ticking away and he shot up out of his seat like it was electrified. He swore and quickly slammed the button on the clock. It took him about two minutes of pacing to get himself to calm down.
In the end, he *still* beat me. When we shook after my resignation, I don't remember him being angry at me. He was simply happy about the win and didn't seem to be holding any grudges.
Do I think I did the right thing in remaining silent? Would I do the same thing if it happened again? Probably not. All these years later, I still feel a little moral taint for having exploited that player's mistake. What I did may have been legal, but it feels a little cheap. Next time? I'd point to my opponent's clock. I'd rather have a clear conscience than gain a meager advantage that may not amount to anything.
*Argument 1: Exploit the mistake.* Every chess player has three resources--material, position, and time--and it's up to the player to use those resources better than his opponent if he expects to win. Managing your chess clock is a basic aspect of managing your time.
*Argument 2: Help the player out.* The clock is a tool that is subordinate to what's happening on the board and both players should use the clock to help them have a good game. It's in the interest of good chess to point out the opponent's error regarding the clock and it's in accordance with The Golden Rule: "Do unto others as you'd have them do unto you."
In one of my first OTB tournaments, my opponent didn't hit his clock after moving. He was a guy in his late 20's, I'd say, and was probably as inexperienced in tournament play as I was. I considered the situation for a moment and decided to use the time ticking away on his clock to analyze the board. I said nothing, but just focused intently on the board. This went on for two minutes... three minutes... five minutes. After ten minutes, my opponent was getting agitated and it was clear he was wondering what was going on: Why wasn't I moving?! Not long after that, he noticed his clock was ticking away and he shot up out of his seat like it was electrified. He swore and quickly slammed the button on the clock. It took him about two minutes of pacing to get himself to calm down.
In the end, he *still* beat me. When we shook after my resignation, I don't remember him being angry at me. He was simply happy about the win and didn't seem to be holding any grudges.
Do I think I did the right thing in remaining silent? Would I do the same thing if it happened again? Probably not. All these years later, I still feel a little moral taint for having exploited that player's mistake. What I did may have been legal, but it feels a little cheap. Next time? I'd point to my opponent's clock. I'd rather have a clear conscience than gain a meager advantage that may not amount to anything.