It's required to edit the individual postbit of a particular member. If you set up a rotating script on a site, and link it as your avatar it won't work. The server will grab an image within the particular folder of the script and use that as a static avatar and upload it to the server for you to use here, rather than using an off-site link. Using the add-on makes it use the off-site link and it rotates the way you want to. But as it stands, postbit edits are specifically staff only. And even then, I think it's higher staff who have it. Luke, Shivi, Erica, Andy, Audy(?), Jake, and myself are the only ones who have one, I think. I haven't seen a moderator who has a custom one.