Ask HN: Are Glassdoor reviews a reliable indicator of a company's culture?

A particularly negative review of a London startup[0] by a former employee has been doing the rounds on social media recently. Perhaps unsurprisingly, a couple of extremely positive reviews by current employees have suddenly cropped up for that company as well. So positive they feel a bit like HR plants. But then again, the original feels like a gleeful hatchet-job and is maybe a bit extreme going the other way.

Is Glassdoor reliable, and if not, are there any reliable alternatives?

[0] https://www.glassdoor.co.uk/Reviews/Employee-Review-ROLI-RVW17219691.htm