Look for reviews that are dated, specific about the situation, such as a downsize, an estate sale or a relocation, and consistent across more than one platform, since a pattern across several sources is more reliable than a single glowing post.
Also weigh how an agent responds to a mixed or critical review, if one exists. A thoughtful, specific reply tells you more about how that agent handles a real problem than a page of five-star praise with no detail attached.
Reviews are one input alongside an interview and a look at the agent's actual pricing process. Get your hand-reviewed valuation from Joel Dyck.