Contributory negligence would decline all coverage if the insured in any way contributed to the event.

I'm guessing the hotel filed a property damage claim with their insurance, who then sued the commenter, whose liability insurance worked things out with the hotel's insurance company.

You're right, the commenter would be covered 100%, but their insurance might have only paid out a fraction.

https://en.m.wikipedia.org/wiki/Contributory_negligence (apparently it’s a similar concept you have in comparative negligence)