Formatting errors are at best an incidental detail that nobody should be wasting time on regardless of where it pops up; if prettier helps, great, but in its absence, I don't believe a trivial formatting inconsistency should illicit more than a tiny note among other problems you'd ask to be fixed. If the formatting errors are so frequent and so glaring as to warrant a negative review on that basis alone, such that you feel a mediator is required, then I'd wager Prettier may be obscuring other communication deficiencies.

That said, I do believe in the value of consistent formatting tools, I just think Prettier is a somewhat lazy choice that attempts to skirt responsibility for deciding on things or cultivating agreement. It's a disfunctional team who's members care too much about their opinions on such trite topics, and/or who aren't capable of coming to agreement on a common set of them.

For PRs, I've always just asked someone to run their formatter if it's clear they forgot, and usually there's a common config used by some formatting tool, it's not worth much beyond a a one-liner to make these decisions, and you should be able to do this periodically as things change.