> Is it taboo to answer my own questions to ...

You are allowed to ask questions and answer them yourself.  [It is a good thing][1].  I have answered a few of mine own.  It is **very important that** if you do this that you **write a good question**. 

> to promote nice features of <xyz> app?

I am going to disagree with the crowd here and suggest I don't really care about the promotion aspect that much as long as the question is actually good, [on topic][2], and not extremely specific so that it only applies to a very specific situation.

If you can ask a good question, then people will probably up vote it and accept it on the site.  If you ask a poor question, and use a good answer that you post as an excuse to ask it, then it will probably be down-voted or closed.

So, ask a question good on-topic question that is as generic as possible, and doesn't have any arbitrary limitation so that only your answer would apply.  Leave it open for a while before you post your answer.

We like good questions, and we like good answers.  We don't like extremely contrived questions that are only asked so you can promote something.

If you are posting crap, then I will down-vote it, flag it, or vote to close it.

So make sure your question doesn't fit into match any this criteria.

> - downvote - This question does not show any research effort; it is unclear or not useful
>
> - too localized - This question is unlikely to ever help any future
> visitors; it is only relevant to a small geographic area, a specific
> moment in time, or an extraordinarily narrow situation that is not
> generally applicable to the worldwide audience of the internet.
> 
> - off topic - Questions on Server Fault are expected to generally relate
> to servers, networking, or desktop infrastructure, within the scope
> defined in the faq.
> 
> - not constructive - This question is not a good fit to our Q&A format.
> We expect answers to generally involve facts, references, or specific
> expertise; this question will likely solicit opinion, debate,
> arguments, polling, or extended discussion.
> 
> - not a real question - It's difficult to tell what is being asked here.
> This question is ambiguous, vague, incomplete, overly broad, or
> rhetorical and cannot be reasonably answered in its current form.
> 
> - exact duplicate - This question covers exactly the same ground as
> earlier questions on this topic; its answers may be merged with
> another identical question.

  [1]: http://blog.stackoverflow.com/2011/07/its-ok-to-ask-and-answer-your-own-questions/
  [2]: https://serverfault.com/faq