It's a neat idea to implement it as an extension. And I enjoy how it just overlays the normal site (loads separate pages as separate pages, etc)
And finally a dark mode. Dear god.
One bit of feedback: it took me a minute or two to figure out how to comment on an article (to write this very comment); I actually had to look back at the website to make sure commenting wasn't a "Pro" feature. I don't know if the reply-arrow really translates to comment threads, especially when you're not "replying" to another comment but to the main post. Some sort of comment-bubble icon might be clearer. At the very least I think those icons could use titles, and/or "modern" tooltips.
Overall pretty cool! I think I'll try it out at least for a little bit
Edit: A couple other things,
- It's a bummer that karma and threads (now "Comments") are hidden behind an extra click. When I'm actively participating in a thread those are two of my most frequently-used parts of the UI
- The thread UI is a little too minimalist I think; it's a little hard to visually parse where one comment ends and another starts, nesting levels, etc. Some tasteful borders or lines would go a long way here, though so would some slightly-more-contrasted colors
- I don't see a way to see upvotes on your own comments like in the main UI. My dopamine receptors would like that feature back ;)