As the moderator here I will say a few facts and a few opinions:
We almost never delete posts. Fewer than 10/month that aren't spam. And when we do, they're often something like four a time, where a member posts something, a moderator replies, the member replies again, and so does the moderator. After a time, all the posts - since they're off topic - may be removed. We have three levels of moderation, basically:
Level 1: Verbal warning in the topic. Usually short, since it's off-topic, and done by a moderator or occasionally just by another member who knows what's acceptable?