Part of the idea is that WE would be helping to promote Webcomics Community, not just that it would promote our comics. Also, it sounds like Rob means the link to go to a page of banners, so it would be promoting our comics not just to people on this site, but to each other's readerships as well.
I have no interest in promoting the site to Webcomic fans. If they don't make or provide services to webcomics then I don't really want them here. The wizard didn't want Dorothy behind the curtain either.
The second half of what Gib has said is the intent here. It will be a place that you can link to that will promote ALL the other comics that participate. Kind of like the Keenspot adbox except the user has to click on the Webcomics Community button to see the ad... and it isn't one ad but banners for all the participating sites.
So if one were inclined to explore webcomics for other, new webcomics, one would click on the button and be brought to a page with potentially dozens of other webcomic banners at which point one could explore all, some or none of them at one's leisure.
It's a link exchange without the exchange. Instead of linking all the people who link to you, you both just link once, to a repository of links.
Have a confused you yet?