Definitively not in "Hydlaa Plaza" unless the creator of the thread explicitly asked for a stricter enforcement of on-topicness.
Also as long as it does not disrupt badly the thread, it should not face harsh measures.
Finally if someone is responding to an off topic post, I would say part of the responsability for it falls indirectly on the one who made the first off topic post(Although I don't see a little of offtopicness as bad, as long as it doesn't become a 10 pages long off topic discussion or something like that).