Well, the concern is that the "2 or more kills landed" message is partly responsible for what is perceived as bad gameplay. What is bad gameplay? An example might be someone who
only fights when in a group or with lots of extra altitude,
always dives to ack when he's about to lose a 1vs1 fight, etc. Everyone does these things now and then. Everyone has ganged, been an altitude monkey, or hugged ack at one time or another. And that's fine so long as it's not rigid behavior, but when it becomes rigid behavior it hurts the game.
Are kill messages responsible for it? I don't know, but when you're new to the game it sure is cool to get your name in lights. It feels like you've arrived.