I can't speak for youtube given that I don't really actively browse it, but I'm not sure how it's "braggy" when the entire purpose of "Show HN" is to demo things that were made by the person posting it (https://news.ycombinator.com/showhn.html):

> Show HN is for something you've made that other people can play with.

At most, it's redundant, but not in a way that hurts anyone.