Its identifiable, yes, but not personal. Otherwise, all free-form text entry would have to be processed prior to a GDPR request, which is not likely.
Take Facebook as an example, when you request your personal data, they present what is linked in their database to you, which is of course not where anyone mentions your name. Who is to say that my name (Paul Smith) identifies me and not some other Paul?
Actually, when someone is identifiable with a couple of pieces of data, that becomes personal data. For example, if you would be the only Paul Smith on earth, we would consider that personal data. If you are the only Paul Smith in the US and the context reveals that we are talking about someone in the US, those 2 pieces together are personal data (and so on).
That is what they mean with "indirect identification" in the link provided by jdietrich.
Take Facebook as an example, when you request your personal data, they present what is linked in their database to you, which is of course not where anyone mentions your name. Who is to say that my name (Paul Smith) identifies me and not some other Paul?