If (1), then shame on you. I think it is unethical to portray yourself as unaffiliated with the app yet promote it.
- The app developer, or a friend/family member, or
- Someone hired by the app developer to shill for them, or
- A private individual who just happens to love this particular app
If (2), then you're even a lower form of life than in case (1).
If (3), then I'm floored. To think that there's someone who has only two posts to their name used both of them to pump up a single app so effusively, while everyone else thinks it's junk, is such an amazing coincidence. Don't you think?
BTW... If you are in category (3) then you really ought to think about not promoting any more apps, cause you suck at it, and you make people think very, very strongly that you're in one of the other two categories, which doesn't help the app developer at all.