I agree with marathon, tk damage should be reflective 50% so you dont die and wonder how you died, say it in the welcome, and then make a message every 5 minutes saying tk damage is reflective, so it will stop all those people like me from spamming and killing a guy in black plate, and taking your team mate down with him orrrr, just make tk do 0% damage to everyone, more spamming faster rounds, but weapon bounces off all team mates you cant spam in a group and you cant tk in a group but 1 on 1 you could have always spamed and you will be able to.
Do not make tk damage 0%, I'd just play single player if that happened it'd be the exact same watching a big cluster of guys all swinging swords into the guy in front of him ... Except maybe less screaming in multiplayer.
FF is an important part of this game, it limits spam, for those who understand that swinging left and right with a huge weapon has a chance to hit your team mates if they're beside you.
We already have enough people who play this game holding the W key and clicking the LMB as fast as possible this would just give them more incentive to run in blindly swinging.
I do agree there should be a TK penalty of some sort, even if it's not super harsh, because obviously TKs aren't all intentional but something to go "Oh crap, I killed my team mate, I lost 5000 xp & 100 gold + he was really helping me out with all these enemies and now its just me." some kind of punishment, even if it's hardly severe, just like a slap on the hand going "HEY WATCH YOUR SWINGS MORE NO NEED TO BE KILLING YOUR FRIENDS !"
Just my opinion
I always feel super crappy when I kill a friend and apologize as fast as possible even in the heat of battle, though sometimes I delay it till the end of the round if theres no chance to stop and type.
Biggest pet peeve is getting team hit or team killed and the guy just going off on his business whistling without a care in the world spamming left to right with his great long bardiche hitting friend and foe a-like.