I don’t consider Devil’s Advocacy to be arguing in bad faith – in its intended form it exists for the opposite reason, to push forward the discussion, and thus tends to avoid the kind of behaviour I mentioned.
If someone is harassing you, that’s definitely not OK.
I also tend toward the policy suggested by @codinghorror and @orenwolf: I’ll combine replies so as not to flood the thread — unless I’m taking issue with something in particular, where I go standalone in reply.