I don’t think mentioning it is inherently racist(y’know, without the added context that it’s fucking 4chan), it’s just that it’s irrelevant, and therefore kind of weird. As they mentioned, if the person were notably tall, that also wouldn’t have any relevance, so unless you’re just specifically calling attention to it because it’s strange to you, which would be racist if used when describing someone’s race, it’s very strange to just suddenly say that they are that adjective without it being necessary for the story.