I think it would help to have some kind of notification on a thread (besides a moderator post) to let a reader/poster know that a thread is having problems with content/etc.
I think that some posters don't see a moderators warning/caution posts until it is too late, or maybe not at all and then the thread is closed. This could easily be due to the position of the post in the thread (previous page) and/or the poster simply doesn't read all posts in the thread and makes a post that just adds fuel to the fire.
Yes, posters probably shouldn't do that - but people sometimes forget themselves in the heat of the moment.
What I suggest is maybe an indicator or a popup when a person posts to a thread that is in that status - something along the lines of "this thread is under warning for content, please think twice about what you post" or something like that before they can click on the "post" button. The same may go for individual posts to a thread.
This sounds like a good idea. A colored box added, edited in, just under the thread topic at the beginning of the thread. If a thread is more than one page a mod could post with the same worded box in a post as a notice for those that may not have noticed the box under the thread title. No reason for mods to pussy-foot around with the "Guys you need to remember the golden rule", or some such. Just the box with "this thread is under warning for content, please think twice about what you post" should suffice. It would be great if something like that would get people to quit feeding the blatant trolls and getting threads closed. Face it, trying to "TEACH" the trolls and trouble makers a lesson, is what gets threads closed 95% of the time. Letting a blatant troll yammer to himself, with no other input, would be a beautiful thing to see.