How so? Legally, I don't see anything particularly unusual about this.

I don't think there's ever been any case law to suggest that online reviews enjoy some kind of blanket protection from libel laws. Whether a particular statement is defamatory depends on a lot of complex factors, but the medium of communication is not especially relevant.

At least in the USA, the frequently-mischaracterized section 230 of the CDA would (probably) have protected Google and Yelp themselves from being sued over their users' reviews. It wouldn't have done anything to protect the review's author. I don't know how Canadian laws compare.