Players attack animations have very wide hit cleavage hit box. Some attacks have 180 degree radius hit boxes that will certainly hit you allies.
In Monster Hunter when you hit your friends, you itnerrupt their attack animations and flinch them, some attacks can “Send you teammate flying” for Flying Attack, other attacks can “Knockback” or “knock on but” * or “flinch” canceling their attack animation and stopping for some time i nplace.
Its fair and adds depth to the combat. Players button mashing ignoring distanceing as part of core combat will only interupt each other and do less DPS than they would in hitting the enemy solo.
*”” Is a Character state .
Maybe it’s a mistake, guess we find out soon 
Coop looks dope though, and the fact that you simply get a dedicated server, so you and your friends don’t have to make sure the host is online, is crazy.
I really hope it blows up, but I think they need other multiplayer features for that, like PvP match making or 2v2 match making or other activities that involves other players than the ones on your own realm.
And a possibility to have more than 4 players in a realm. Or maybe have a dedicated “market place” realm where you can go and trade loot with complete random strangers, stuff like that
Video example. I will add more:
Friendly interuption “Knock on but” character state
