if you dont know what a signature is. its a picture or block of text that you can add in with each message.
its a simple thing to enable,rather secure for the servers end as you all don't handle any of the image hosting or links.
its cool and allows people to show a little bit of there personality with each post. This is one of the only BBS forums that i've seen that doesn't allow it.
Although im not sure if you all are on some sort of bandwidth cap per month. but most combat that (and excessive mouse scrolling) by limiting the size of the signature to something like 195x350 and Not allowing .gif (video pictures)