Originally Posted by Durzaka
There is the difference.
When it is obvious the ADC is gonna get the kill, landing the last hit for no reason is stupid.
If the ADC is chasing, and the enemy is just inside his range, then its fine, better to secure the kill. But if you dot he same thing and the enemy is like 100 units from the ADC. you just took gold from him.
The problem is that this is the new player forum. To know that the ADC has burned flash, any other escapes, and is guaranteed to not have backup (say a Kayle/Zil ult, or even just one or two enemies converging on your position as you chase for the 'guaranteed kill'), takes a lot more than you can reasonably expect from anyone who is posting in or reading this sub-forum.
If you're talking about high level play then sure, but at high level play they don't need to be told that because they've learned when someone is 'assuredly dead' by experience. (And hell, even pros get it wrong and miss out on a kill because they're trying to squeeze every last ounce of gold for their ADC out.)
A dead enemy means one of your lanes gets to free farm (or all of them are safe from ganks if it was the jungler), and one of the enemy gets zero gold and experience for a bit. A dead enemy is the only good enemy, and telling new players to complain about killstealing (even situationally), is really detrimental.
Note, expending long cds needlessly (using a Karthus ultimate on someone that is 'guaranteed to die' when you could have just waited to see if they got them), is different. This is bad, but not because it is 'kill stealing.'
This is bad because your team is now down that cd for the next few minutes, leaving the enemy a bit safer.