I would consider this a bad sign. My wife recently left a company that had few reviews. The management would actively try to remove bad reviews on any basis possible, and have been successful enough at it. If you look at her (small company's) page, the reviews tend to be very polarized- "Great Place to Work!" "Keeping it 100!" to "Miserably failed at just about everything" and the reviews tend to be 5 stars or 1 star. There is not a single 3 star, and only 2 4-star reviews for a company rated overall at 3.4 stars. HR is almost certainly seeding it with good reviews, and several employees have had their reviews pulled, resulting in their reviews not in any way resembling a normal distribution.
Anecdotes aside, I think there are real tells:
-Review numbers being "hollow" in the middle.
-Data not quite adding up- for this particular company, No one has hit the "approves of the CEO" button, but I once looked at a startup that was quite the opposite- 85% approved despite a middling overall rating. Was the founder just beloved? Its hard to say, but I found the lack of matchup concerning.
-Are a significant number of complaints consistently in certain areas? Work life balance bad, bad leadership, etc... if so... these are probably true, and people not mentioning that may need closer examination.