Thanks for clearing things up, Kent.
Regarding copying and pasting public domain content, it's always about publishing the most helpful content on your blog. It doesn't always have to be original, just useful. Therefore, if you find a public domain content that offers relevant information to your readers, I don't think there's any reason not to copy and paste it on your blog. You are well within your rights to do this, so if you feel you're doing the right thing, then you should.
However, I did fail to mention that you should attribute your sources just to inform readers that the copy and pasted work came from a public domain work and to avoid confusion in authorship.
I hope I answered your concerns about my post correctly, Kent! :D