[nemine]

My opinion: i don't see the point in doing this. sorry ^^;
The spoiler-tabs are created for a reason, and people should already know that spoiling should only happen like this:

Spoiler

remember people, that even tho there would be different threads to those who watch raws, those who watch subs, and then those who are either anime- or manga-only, people still watch/read them with a different pace. you might be already waiting for the newest bleach etc., when your friend could only be starting with the series. So stop spoiling the fun, and hide your interesting convo

well of course the problem is that not all people respect the others, and continue spoiling without mercy. so, even if your suggestion goes through, it won't change the spoiler-addicts. They probably will continue spoiling. and then there is also the issue of a "spoiler". what is considered as one, and what not. Some people might not know what is counted as a spoiler.