When you play a poison champion like Singed and you die, and a champion after you have died walks into the poison cloud, any item you bought can not be refunded anymore. This is extremely obnoxious and should be addressed eventually.
Deep Terror Nami2 votesIt's not a bug. Your abilities that are still out will benefit from those items, so to prevent abuse (like buying AP for a little extra then refunding it for what you really wanted) you will be unable to refund items after damaging an enemy.
Gilgamesh1 votesThat requires such intense speed and planning, that it is almost impossible to pull off making it actually something that should be rewarded if that was actually the case. Instead, just don't make it possible in the first place, and allow to refund items. Where did Riot say that this is an intended feature?
Deep Terror Nami1 votesYou're thinking of a limited selection of abilities that aren't out there very long. Try thinking of traps and DoTs, or launching a global Ult from the fountain.
While I'd like to get you one of the sources of this, I don't really have that kind of time; the keywords to search for that are too vague. Sorry.