I think (Correct if if I'm wrong) the suggestion here is simply that if you are about to make a post that *you* feel is going to veer the converstion off to some other worthwhile discussion *you* should just start a new thread. Done that way IMHO it would be a better course of action, namely because the useful side stuff would be seen by those who may not intrested in the orginal thread and be intrested in or have good info on the side topic. It also makes the side stuff more visable to those who search for it later
I belive this was made as suggestion for monks to try when they are in this situation as opposed to a hard and fast rule enforeced by anyone, bear in mind that a lot of how this site works is based on newcomers follwing what those who have come before have done and thus far I think that has worked suprisingly well.