The pull request view shows an index of commits included in the request.
The likes badge should display as green with a alt text of "You have approved this commit" for commits that you have approved. It only displays this way if you are the most recent reviewer to have approved a commit.
To recreate: Have another user submit a pull request Visit a commit, approve it, go back to the commits tab of the pull request, see green check-mark badge. Have the author approve the same commit. Refresh the pull request view, see an increased likes count, but with a grey check-mark badge.