I try to always look at this from a common sense perspective. Would a citation or brand mention be useful for a human? Yes - if it is in the right place. It helps build awareness, credibility and trust. Search engines are just trying to model what is useful for search engine users (humans) so these signals are most likely factored in. A quick dive into the PageRank Wikipedia page (https://en.wikipedia.org/wiki/PageRank) talks about how the original PageRank algorithm was informed by Citation Analysis studies by Eugene Eli Garfield. Citation Analysis looks at the frequency, patterns and graphs of citations in documents and uses the links from one document to another to help assign value to documents (pages). A stated goal here was to identify the best (most important) documents in a set and Google is working with a huge set of answers for most questions so citation analysis, links and many other factors must all be looked at here. This is a bit of a grey area. Citations and brand mentions are not links. But citations are a huge factor in Local SEO - why would they not be used, in other ways, in more traditional SEO? We could likely debate the specifics until the cows come home (and still not know the answer) but certainly I believe that citations and brand mentions add value.