This feature doesn't seem to be working right now. Threads with multiple Blue posts don't have the icon so I can't skip from one Blue post to the next, even though there are multiple blue posts and the threads aren't locked or anything.
I am also experiencing this. In threads where I know there are several Blue posts, the "Jump to next Blizzard post" icons are missing. Only the first Blizzard post is accessible using the "Jump to first Blizzard post" at the top of the thread, but all other Blues are no longer easily found.
Confirming this. Tried using it in the beta class balance analysis thread and am unable to do so.