Exactly. If you want to comment in full agreement like a "this" comment why not think of another point that adds to the point you agree? Maybe state why you personally agree; or even restate the point from a different view point. There are tons of way to make a decent meaningful comment.
Yes, it says you agree with the comment. Although, I always thought it was an useless statement. If you agree with a comment, upvote it, no need to "this" it.
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