At the ”State of Search” search conference in 2017, Google’s Gary Illyes made comments about Google using sentiment analysis, which is “the process of computationally identifying and categorizing opinions expressed in a piece of text, especially in order to determine whether the writer’s attitude towards a particular [business], [website], topic, product, etc., is positive, negative, or neutral.”

For a 2nd time today @methode said Google pays attention to negative sentiment about your site online #StateofSearch

— Mark Traphagen 🌲🌲🌲 (@marktraphagen) October 10, 2017

Gary’s comment was somehow misunderstood, but Mark Traphagen confirmed that he discussed this with Gary:

“I was in the same conversation as Kenichi, and also talked with Gary on my own, and I think Kenichi oversimplified Gary’s qualification. Gary said was reluctant to call it sentiment analysis, but confirmed that if there are a lot of mentions of a brand, positive or negative, they COULD (not necessarily will, but could) affect how much Google trusts that brand for SERP ranking. I think part of the problem might be that Gary didn’t fully understand what we meant by “sentiment,” because when I put it more simply and said, “so a brand getting a lot of negative mentions could be less trusted for ranking, and one getting a lot of positive mentions could be more trusted,” he said yes, that was correct. source

So, apparently, yes: brand mentions are a ranking signal.