You are naive if you think an insurer is going to pay out for damages resulting from the formation of an illegal contract (between renter and subletter in this case), which is automatically void.
This might be old-fashioned, but I think that the very act of commenting in a thread carries an implication that you intend your comment to be relevant to that thread.
Doesn't matter. Even if such a general product existed it would be easy for an insurer to decline payout in an instance such as this. I'm guessing AirBNB will be reluctant to pay out here for similar reasons, unless it emerges that the party organized have a history of this sort of thing and AirBNB knew about prior complaints at the time they brokered the booking.
