Well, since it happens on the last post on a board, the "dimming" is meant to tell us that the link leads to nothing. Like the faded "next", which now has an underline, but didn't--when there was no "next"--before all this began.
I think the solution to both problems would be to remove the fade--how visible is it in some lights and on some devices?--and fix things by simply removing the underline when the post is the last on the board.