Seems like it would just kinda clog up the forums to have a thread dedicated to one particular comic constantly popping to the top of things from bumps? And I don't think it'd really drive any traffic to your comic...
Instead of bumping a dead thread, I'd recommend you put a link to your comic in your forum bio, then just interact in interesting threads with other people. When you say interesting things, interact with people, act as part of the community, people will click on your name, see your bio, and BAM, they're clicking the link to your comic because you're an interesting person and they actually want to know what you make.
And you know, you can still post links in relevant promotional threads, and look for relevant places to draw attention to it. I'm of the belief that the more organic your interactions with others, though, the more likely you are to get subs.