ZDoom

Related suggestion: would an alternative "actor hits floor" sector action type that detects players on edges be doable? That'd allow the OP's suggestion to be done via a small script and allow for tons of other possibilities (bouncing scripts with ThrustThingZ is my current headache).

[if "sure", will make a new thread of course.]

The sector damaging stuff has always worked so that it only apples if the CENTER of the player touches the floor. For obvious reasons this is not going to be changed, even if it makes little sense in this particular case. This is the stuff compatibility nightmares with older maps are made of.

Not so much intentional but an artifact of sector properties. You sector effect is that of your exact center, and thus only one is ever applied at a time, and has been the case since vanilla. A compatibility flag would likely need to be introduced for anything to change about it.

See this very old zandronum ticket [url=http://zandronum.com/tracker/view.php?id=955]here[/url] (yeah, I'm not sure to know why the reporter didn't make a bug report here at that time...).

Load zdoom with the provided example wad, move the player on the edge of the sector (which is in an higher place than the rest) and make sure the player's center is not inside the sector. Then the script will change the sector into instakill, but the player doesn't die.

Is this intentional?