I've noticed as of 1.8 that I can't use MMB to do a punch attack, where your character punches with their left hand, while holding a grenade or the knife. I also can't do the "melee charge" where you press MMB while sprinting with the knife/grenades either (works with other weapons). Someone on the Sandstorm Discord said the ability was removed in 1.7.1 when the new knife animations were added but I'm almost certain I've used it since then, it only stopped working in 1.8....

I didn't see anything in the patch notes about it so I presumed this is a bug. Either way it's a pretty big nerf to melee, you can no longer stun enemies by charging into them nor can you do the slash-punch trick (where you slash with the knife then punch right after) to get 2 quick hits. Imo that wasn't particularly overpowered, it added a bit of skill to the melee combat at least!