The news on this broke yesterday evening, and at one point both threads were on the front page. In my opinion the time to mark one as a dupe of the other was then, not 12 hours later. Especially in light of the fact that the 2nd comment on the now-marked-dupe post was a link to the earlier discussion, and in spite of that, discussion gravitated to the submission linking to github over the one linking to facebook's PR response.