I also didn't know there was a dark mode, but if you ever find a website that doesn't have one I highly recommend the Dark Reader browser extension, I've been using it for years and it's never let my eyes down.
I had the same issue as OP so went to check my language settings… it was set to “undetermined”. Then I realized that despite it being radio buttons, you can select more than one. So I added English in addition to Undetermined, and now I see the missing 4 comments.