Actually, since Glassdoor's protection can obviously be compromized, anyone posting on their site should do so with Tor Browser, which anonymizes access by routing traffic through a minimum of three relays in the "dark web" of the Tor network. It might also be wise to do this on a public WiFi network (not your own ISP or mobile data provider).
Any email provided to Glassdoor should be a burner on a service that is not one of the majors (no gmail) also set up with Tor browser, specifically for Glassdoor (and used for no other purpose).
Finally, the text that is posted should be somewhat disguised if possible, with altered vocabulary, atypical slang, and distinctly different grammar and sentence structure. Any facts that can reveal identity should be removed.
Under no circumstances should a native Android/iOS app be used to post or access any such review.
It sounds like we will have examples soon of what happens without these precautions.
I imagine that many reviews will be coming off Glassdoor's site rather soon.