So here is my opinion. I use other sites for a while but Glassdoor came to my eyes, so I thought it good to post a honest review on my company. It was mixed review with good and bad and what can work. I read their guidelines, and followed what they say. I made sure they are well written. Then, the review was removed by moderator. No feedback or any. I went back to their guideline and rewrite several times, same thing.
When I look at the reviews posted in Glassdoor, all are short, rough or lack accuracy. They are aligned from good, so good reviews catch eyes. Filtering works similarly. So review quality is no good, do not give an inside look and even gives a false impression. I searched the internet, I found quite a few complaints about similar situations.
When Glassdoor removes honest and informative reviews, they are just giving a false impression. The quality of reviews varies, so moderation is not done the same way for all reviews. I see Glassdoor reviews are censored or manipulated passively by that way, so it gives biased reflection of employee reviews. I thought they are reliable, but not anymore.