Every game I've played has had this feature. IT's so annoying as a cleric to try to cast gifts on someone when they have full or partially full gift slots already.. plus you don't know what already-existing enhances, raises or surges they have.. so you could actually do more harm than good by casting on them. And it really hurts the whole point of ninja buffing!
The person casting buffs should know if those buffs are alread on that person. I think this should be a toggleable feature under a menu (or just given an activation script like /buffs until the rest can be dealt with).. use it if you want type thing...
But knowing what buffs are on the person you're trying to cast on.. or at least knowing if they've got something funky going so a pure would be in order is pretty much a given. I'm sure they'll have this at some point.
Does it need to be all the same icons as the characters have on them? I can't see how it would work without them... it seems, from a coding aspect, that would be the easiest way to do it. Granted you can already see their health (the exact number even) so people can't complain that this isn't RP or useable since they already know "magically" that the person has exactly X pints of blood left. So they'll just "magically" know what buffs/debuffs are cycling on the person at that time as well.
This is a must have if the game is getting back on it's feet.