I like this UI better because it's more compact than Photon, but I like both so far because it's easy to turn on dark mode. I also like the previews better than old.slrpnk. I like how Alexandrite discussions open up in something that lays over the rest of the content, and I could close the sidebar to get a better view. I'd like it better if I didn't have to scroll back up to the top to close the discussion, but maybe that's a work in progress or something I could post as a wish on their development site.

PS—Oh, I can just press Esc. Oh, I think there's also a navigation bar that will let me close the thread.

Also, I like how it shows the number of unread posts since my last visit, but I don't think there's a way to either take me to these posts or to highlight them while I'm scrolling the thread.