Typing this using the extension. I like it, through I think one of the reasons I like browsing HN is that the website is intentionally very simple / I don't have to think around navigation at all (everything is very linear, I click something I get a page reload with the thing I'm expecting). This adds just a bit more cognitive load around navigating.

I'll keep using it for a bit to give it a fair shot however since I can imagine the split pane being super useful in certain cases.