They make very difficult for employees to post honest negative reviews. They will simply remove your review claiming that violates community guidelines without pointing out specific reasons or passages in your review that violate such guidelines.
Contacting help desk doesn't help much. They seem to barely understand English. You get a very strong feeling that messages from customer support are heavily scripted. I googled for the person specifically replying to my complaint and I could not find her on Linkedin. But from the name, I don't think the person is a English native speaker.
If you make any specific questions, staff simply won't answer. All you get is scripted gibberish. It's like trying to start a conversation with a voice activated toaster. They surely don't seem qualified to moderate reviews.
Beware as they are tricky: They will approve your review quickly and remove it a couple of days later without any warning to avoid having to engage in a discussion with the reviewer. I know of people that weren't even aware that their negative reviews had been removed.
I did have a couple of reviews published after submitting several times with minor re-wordings, but takes a large amount of patience.
I would say that if other people are having the same hard time publishing negative reviews on Glassdoor I'm having (and they seem to have, just google), people should probably take any negative review published very seriously.
Also, if you are careful analyzing reviews, you will find many one-liner reviews with 5 stars right after a negative review is posted. These look suspiciously fake. Their purpose seem to be pushing negative reviews to the back. It's worth to mention that the company rating do not take in consideration the number of times it was marked as "Helpful". It's simply the average of all reviews no matter if they have been marked as "Helpful" or not, so take company review rates with a pinch of salt and always read the reviews carefully, specially the negative ones.