If you want to bookmark an article on HN, you don't have to leave a comment for the purpose of tagging it. Just upvote the story. Then goto your profile and cli

If you want to bookmark an article on HN, you don't have to leave a comment for the purpose of tagging it. Just upvote the story. Then goto your profile and click on "Saved Stories." Every article that you've upvoted on HN will be there. Or you can bookmark the page using your browser/bookmarking service of your choice. Either way it's better than leaving a "tag" comment.