<p>I agree that it is better to provide an answer for otherwise unanswered questions.  </p>

<p>In general, if there is an answer in the comments that is substantively the same as the answer I would have otherwise given, I just go ahead and give my version despite the fact that it already exists from someone else.  They had the opportunity to convert their comments into an answer if they had wanted to.  </p>

<p>If you are uncomfortable with this, another option is to just copy the answer from the comments and make your answer community wiki.  You don't get any points for it, but the question is answered.  You can find an example in which I did this <a href="https://stats.stackexchange.com/a/109917/7290">here</a>.  </p>
