"This" when used by itself means the poster agrees with a parent poster; it's an obnoxious upvote really. "This" when used with a preceding quote means that the

"This" when used by itself means the poster agrees with a parent poster; it's an obnoxious upvote really. "This" when used with a preceding quote means that the poster agrees with the quote in particular. Such usage is more of an upvote for select part of the comment.