If a person has posted a completely bogus bad review, I, as the maligned merchant, have three choices. I can ignore it. I can post a response. I can sue the person.

I think it is quite reasonable for Yelp to note when merchants use the third option. As a consumer reading reviews, I learn slightly different things when I see:

A: Three good reviews and one bad review; the merchant responded to the bad review and their response sounds well-reasoned.

B. Three good reviews (one deleted review, but I can't see that) and one note from Yelp stating that the merchant has used the legal system to suppress reviews.

I do think it is important that since Yelp (not a customer) is making the statement that the legal threat was used, that Yelp take reasonable steps to ensure the legal threat actually occurred. Otherwise, a malicious user could falsely report receiving legal threats from a business as a way to harm their reputation.