New Post view and Unread Updates don't work well with "go to comment"

These tools end up being quite similar, and have the same basic issue. When I look at a big thread, like say this one, there's tens or even hundreds of things I haven't read yet. The initial display is quite nice.

The problem comes up when I see a comment that I'm interested in. I click on it, so that I can see the context of who it was in reply to and any replies it might have. When I click "back", I expect to see the same list of posts I was just looking at, but I find they've all disappeared.

A variant of this problem also exists if I'm moving my reading from device to device, or if I close my browser window for now and want to pick it up later.