Ask HN: Can we get the links to be greyed out after visiting them on HN?

I'm not sure what you're asking - for me, on both desktop and mobile, HN Links I've visited (external stories and Ask HN type) do grey out after I visit them.

And I do find that helpful - most frustrating when I switch from one to the other, so the mobile tells me I haven't read an article that I read on the desktop.

I switched to using Safari because of this feature. It even syncs the visited status between devices.