Honestly, I don't think there is quite such a problem with "first posts" here as on some other sites, although that is probably more related to the nature of the site and the general level of maturity of those participating herein. The "first posts" I see here are generally helpful, unlike those on other sites I have seen. I have seen mention of it before at least once in an article (which I can't recall at the moment) on (I think) XP whoring, though.

If I am thinking of the same article you are, the first response was dated 3 minutes after the article was posted, the next two responses were dated a minute later, and the original author responded within 14 minutes of his original posting to thank the respondants for the assistance. I think all three used a similar approach, although I think that was more due to the way the question was asked and the problem space than anything else, and each, iirc, added additonal information to the solution in their explanations.

I don't know that a button like that would be helpful, though, and I would think there may be a small window where concurrent additions could still occur. Just a few thoughts.