Evil players will know what I'm talking about. You're fighting in subdual mode because you think there's a chance that you can turn your violence into a warning, a robbery or some other malicious RP that generates plot content without sending someone to Kelemvor's Wall. You knock the guy down, he logs off.
In fact, I've found myself using subdual less and less as a consequence of these bad actors. Subdual loggers make killing people consistently the better option.
It's a well known fact that some people choose to ignore or opt out of PvP and retcon their own stories whenever they die or even get beat up. People will sometimes state this openly. This is kind of like walking down the street and telling a robber aiming a gun at you "No thanks, I don't acknowledge your existence or the consequences of your actions".
The suggestion: If you log off after being subdued, you leave a corpse and are sent to Kelemvor's wall. I would also suggest that the same thing should happen if you log less than ten seconds after receiving damage, because logging off mid-beating but before being subdued is a problem as well.