Most people who do this style of promoting are rather new and don't yet know what's okay and what isn't.
They know that their comic isn't doing as well as they think it should do (and they probably put a lot of work into it, which makes it very personal to them) and want people to see their work.
I'm sure everyone knows the feeling of being new and unexperienced and just wanting to do your very best.
This of course doesn't excuse poor behaviour on their part, but it also doesn't mean we should hate on them.
If it's too much and a nice discussion topic gets undermined by these hit and run mycomicisamazeballs posts, I don't see why it wouldn't be appropriate to just adress it. "Hey [user], it's nice that you want to share your comic, but this topic is about XY" or something similar should do the trick.
Remember that unlike other comic forums, tapastic doesn't give one the ability to put a link to their comic together with a picture in a signature, so the only way to know about a user's comic is to either click on their profile and hope they linked to it, or to manually search for their name on tapastic. That might very well be part of the reason why people spam the links so much.