Since the stackapps FAQ doesn't really address this, and everything I list below could be acceptable when there is so much to discuss, is there an accepted etiquette to what "answers" should address in relation to app "questions"? It looks like "answers" (and comments) to app postings fall into myriad categories.
- Bug report
- UI guidance
- Feature request
- General feedback
- Full-on reviews
- Project updates
- Follow-up questions
It may be worthwhile to outline this a little better in the FAQ to help direct the parts of the discussion that are best left as comments and those that deserve to be left as answers. As it is, all of these tend to show up in both locations. Of course, since apps are slightly wedged into the concept of a question, it only follows that the answers may not need to be under any sort of suggested restrictions.
One potential is to suggest general feedback (e.g., "Awesome tool!") would be best for comments while things that may require some back-and-forth should all be fair game for "answers". Unfortunately, directing any type of response to one location or the other will likely result in distractions to the overall system.
Bug reports as answers can linger on well after they are resolved, detracting from any current discussion. Complex bug reports as comments can bulk up quickly as details are worked out. Without knowing the system behind the popularity, one could add to your own app as a "answer" with updates and samples (vs. edits to the original question) to keep it higher on the list.