Just checked and yup, all the planted five star reviews are at the top despite having no more than one "helpful" reports. Negative reviews with up to ten "helpful" reports are on at least page two. This is while sorting by "popular".

Seems to have taken the opposite strategy of Yelp, which bumps one star reviews to the top and makes companies pay to hide them. Or my ex-company is already paying, it's hard to tell.

Are they an "engaged employer" in the top right corner? If they are, my theory is that translates to "paying customer" hence the weighting given to the positive reviews.

Yes, they are. That theory makes a lot of sense tbh