<p>Lately I've been perusing old, unanswered questions when I have a few minutes. I come across ones like <a href="https://stats.stackexchange.com/questions/130832/explanation-that-the-prior-predictive-marginal-distribution-follows-from-prior/164974#164974">this one</a>, where the question is more or less fully addressed in the comments. Since these are very old, OP interest is of little concern. But it seems to me that for the benefit of anyone stumbling onto the question, an answer may be worthwhile.</p>

<p>My approach was to answer, with a credit to the comments. But, I'm curious, is there some standard etiquette for answering old questions when a comment-answerer seems unlikely to write a full answer?</p>
