An academic paper should cite sources because such a paper makes a claim to originality of its own. So it is 'bad form' not to cite sources because you would b

An academic paper should cite sources because such a paper makes a claim to originality of its own. So it is 'bad form' not to cite sources because you would be implying that their work is yours. A blog post does not necessarily claim originality and in particular this one does not, it's showing how a proof can be automated. Of course, it's a good idea to cite sources anyway and it's a convenience for the reader, as well as a courtesy to the authors. But it's not a moral failing. If blog posts were as onerous to write as journal articles, there would be no advantage to blogging.