When you comment but dont vote its kinda spammy so I will flag this.
In case you are going to say its not spammy I will explain what you know full well. You say its a good post merely in the hope of getting a comment upvote.
Its so cynical. It would have cost you nothing to vote and comment. Yet you chose not to So I choose to flag. When you are genuine in your interactions with others they will remember you and visit your blog even follow you. When you do this they remember that also and not in a good way.