Thanks. This is a known bug: you technically CAN hold any of the attack keys to keep attacking but periodically the attack will be a dud (does no damage and the animation special effect won't play). We didn't have time to fix this bug before the game jam deadline, but I'll put that on the chopping block for after the judging is complete. Thanks for your input :)
Edit: also, the planned gamepad support should help with that as well.