I made a web app that has arrow key navigation. It might not be the solution to all your problems, but I’d be curious to know what you think of the movement. The arrow navigation is only on top level comments for now, but that’s something I want to work on

https://hackernews.life

I'm curious why you need navigation like this. Is it like selecting text while you read? (I didn't know that was a thing until I read comments about that.)

I find it easier to just read the comments.

I doubt the official HN will ever add this feature, but it seems feasible as a TamperMonkey script or even browser extension.

I will consider including a feature like this when I rewrite https://hw.leftium.com

If there’s a feature you need, maybe write yourself a user script with greaseMonkey.