The push back applied from attacks is not added on the client side. Only the server is aware of the push back which can result in slight teleporting in movement when getting hit. This is not so bad, however the server only corrects your client side position once you move again. If you were to stand still and get hit and pushed on the server you wouldn’t move on the client but have moved on the server. Due to client side hit detection you could get pushed around a corner for everyone else yet on your client still see round the corner and hit people. I have not tested but I believe with friendly fire you could sit at a tight angle on a corner and get your teammate to melee you and push you around the corner but you’ll still be able to see people and shoot them whilst they cant even see you, this could be very bad if a sniper was to watch a window and get pushed out of sight but still be able to see and hit people.
Example:
http://images.akamai.steamusercontent.com/ugc/275093400410374948/4D8AD172CB322A0DA3B68D8A2433516BA851EC78/ - where I was on my client, still able to hit enemies and apply damage
http://images.akamai.steamusercontent.com/ugc/455236878705800420/E401B1A19F6BB8678E8F7515CEB3E90646B1DF31/ - where I was on the server and to everyone else (teammates perspective can see my name behind the wall)
The screenshots weren’t at exactly the same time so it may not be the best evidence but it should explain what I mean well enough.