That sounds good. Is it just something that would come up that people would have to read the first time people come in here, and not every time they read a thread in this section?
If it's only once, the only thing that might be a problem is if people use the "Unread Posts" to look at new threads, rather than clicking on the section itself to read threads, as I know half the time I don't pay much attention to which section threads are in that way - so you might still get people reading and replying to threads without thinking (although you'd hope that people would check)? Sounds like a good idea though ...I'm half asleep this morning and probably not making much sense, sorry!
I see what you're saying Sam's mum and I think the insensitive comments are made through people reading the threads through the unread posts method and they don't really which section they are actually posting in. I may be wrong though - it was just a thought that came to me after reading your post.