In other games, even if you joke kill a guy, you’re still alive. You’ve inadvertently caused someone else to have less of a fun time. That’s where the tf2 killbind comes in. If you do a taunt before immediately killbinding after a kill, it serves to say “hey, this isn’t a serious kill lol”. The killbind effectively changed the Taunt into the polar opposite of its namesake, serving to make the other player laugh or at least smile rather than mald and seethe.

When you kill an opponent, the camera rests for a few seconds, before going to rest on a frame of the person that killed you. Plenty of other games, such as Overwatch or COD have similar things, but those show HOW you died—the past. TF2’s death camera is a still frame of their present, how they are after they killed you. Moreoften than not people just keep playing like normal, others may taunt to incite you with anger. There’s the magic of the killbind. Going to that camera frame and seeing your killer either ragdolled into a funny position or mid-bloody explosion takes a lot of anger out of the killed. And it doesn’t hurt to killbind because you’re effectively choosing to die on your own terms. It’s effectively a choice to remind everyone involved that it’s Just A Game.