If you quote a blogger from their post, do you have to tell them? Should you link to them? In theory, blog posts are public domain, and can be used at whim.Ah...the Wild West of the internet. Do people still feel like everything they find online is free for the taking? Then I recommend a short course of Wikipedia - hang around there a while and you'll learn the basics of copyright. Work done by U.S. government employees as part of their official duties is in the public domain. Really old stuff is in the public domain. Other than that, it's safe to assume that the things you find online are not in the public domain. They're covered by some form of copyright (even if it's a copyleft copyright, it's still not in the public domain). Any legal rights that you have not explicitly surrendered are still yours.
Of course, Burr (or the participants in the discussion) might not have been talking about the "public domain" in the legal sense.