OK, so on HN, it's clickable. But "gray text without underline" isn't always clickable on HN. This is true of other sites: it isn't even clear that the timestamp is clickable at all, let alone what'll happen if you do click it.
Why not acknowledge that this is a problem and just add a little "Permalink" link, which some sites used to have? Or at least a permalink icon?
Surely the combined design talent of Google, Facebook, and Twitter can solve this problem better.