What does "reserved" mean when someone posts it on a mod thread

[kh99]

Does anyone ever use it? I get the idea that it's something that someone thought was a good idea at one time, so everyone started doing it. I don't know, maybe I just don't get it. But I think if I had something important to add I'd put it near the top of the first post, and in red, because some people don't even read through the first post as it is.