I just received the reviews of a paper I submitted. The paper was reviewed by three anonymous reviewers, two of the reviews provided valuable insight suggestions and comments. However, the third reviewer just copied text from the paper. Should I care about what the third reviewer did?
As you've described it, this sounds rather odd. Reviewers are under no obligation to accept a paper to review, so to accept one and then submit what sounds from your description like a complete cop-out is strange behaviour. It's also a bit odd for the editor to send you completely uninformative comments. It's possible that they genuinely did write a review, but that the text has been copied mistakenly, either by the reviewer or by the editor. It might therefore be worth sending a brief email to the editor to enquire about this review. Something along the lines of: "Thank you for consideration of our paper. In the copy that I received one of the reviews does not contain any comments, only text from our paper. I just wanted to double-check that the correct version has been sent through, in order to make sure that I can respond effectively to all of the reviewers." Be very polite, and make sure you phrase it as a request for clarification, rather than a complaint.
If it turns out it was their genuine review, you are of course allowed to care - it's a bit frustrating if one of the reviewers has not fulfilled their role properly. But it's not a big deal, and there's not much that you can or should do about it. Some journals only get comments from two reviewers anyway, so just think of it that way and ignore the third.
Why should you care? One function of a referee's report is to explain to the editor what the paper is about.