As I've said on threads on the past, there's a serious issue with how Tapas' "popular" and "trending" sections work that make it basically impossible to get seen without having an audience to begin with, and make it pretty much a necessity to get a staff pick or similar in order to grow to the point where you can actually be discoverable at all. Popular runs on how many likes you've had in the last day or two, so if you're not already hugely popular, you're only likely to appear on update days, and the more followers you have, the easier it is to get and stay on that ladder. The top two rows of my genre (Action) are generally practically all Tapas originals, with the benefit of regular promotion, and I've only ever hit that top row when my comic was a staff pick.
Trending tracks something like comments or new followers and is basically inaccessible to anyone who isn't either really, really new or already massively popular. As I've said before, generally the Action genre doesn't even have enough "trending" comics to fill a page.
The problem with limiting promotional threads is that it'd be treating the symptom, not the cause.