Again, intent to use it ever does not mean each use is intentional. And note that I am not saying accidental use is rampant, or even common, just that it's possible. But as you (or someone) noted, accidental use is worth at least an "Oops," if not an outright apology. Another case where the effect (although not the use) is unintentional is for one of the AoE pranks and the player can't see another player is near enough to be affected. Again, not prevalent, not common, but possible.
Seriously? It's impossible to open an inventory bag and use the wrong item? What paragons of perfection you must play with.
Possible does not equal probably. Nothing is imposable, a lot of things are improbable. Both of your "not impossibles" are highly improbable. Considering you have to have some one targeted to not get a "you need a valid target" error, how do you accidentally target some one, then accidental set off an emote. This gets more improbably by the moment.
If I fire a shot gun in to a crowd no one accidentally gets hit, whether they are the target or not, I purposely fired the shot gun so it was no accident.