Lucas Blackstone
Explorer
A rope has no damage dice. You never roll any damage with it. That is what people mean by it does no damage. In the D&D sense of how much damage did you do with your rope attack. Zero.
If you're doing zero damage, then you're not strangling anything.
Um...yes you are. That's why the suffocation rules exist... It isn't HP reduction but an alternate way to subdue.
But anyway, RAW says lycanthrope are immune to non magical non silvered weapons. I've shown that rope is a weapon. Ergo, the lycanthrope in question is immune. You can rationalize it however you want. The rope cannot constrict the airways of such a magical creature or what have you.
It's like saying you can beat a wererat to death with a club because the club isn't damaging the wererat, but just crushing bones within the wererat.
Damage refers to hit point reduction in the rules. If the DM rules that rope is a weapon, perhaps doing 1d4 bludgeoning damage, it does no damage to the wererat because it is non-magical and not silver.
But nothing in the rules says you need to reduce hit points to deprive a creature of air and bring the suffocation rules into play. It appears you're just using the rules as a non-magical, non-silvered bludgeoning weapon to beat down the hypothetical player's tactic because you don't like it. And that's fine as far as that goes - you're the DM and your ruling stands. Let's just not pretend you're following RAW and others are not.
RAW states lycanthropes are immune to non-magical non-silvered weapons. I've already proven rope is a weapon. I guess you're saying that the rope is being used in a non-damaging way. However, I think anyone who's hung from the gallows would disagree