This type of spam seems like the comment equivalent of "native advertising", where the goal is to trick the reader into believing that it is organic content when really the point is to sneak a brand impression upon them.
Most of the comments they're quoting aren't even that. They're purely an attempt to get sneak a link in as the "author" of the comment -- WordPress makes the username a link if the user provided a URL with the comment. The content is irrelevant, and is present primarily to try to get past spam filters.