Well...it's kind of like looking up therapists online, isn't it? If whatever is out there on them is fair game, the same applies to posts on public discussion forums.

I think intellectual property rules are satisfied so long as there is proper citation, which there isn't in the blog MD referenced. The APA style guide even has citation rules for online discussion posts, though having an author with a username that's not their own does look weird. (Atasket, atisket. (2018) etc.)

But yes, be careful.