Many cartoonists draw themselves into their work. Bill Waterson looks like Calvin's dad. Jon Arbuckle is Jim Davis' alter ego. Robert Crumb, Chris Ware, Moebius, they all draw impressions of themselves or alter egos into their work.
Here's a picture of Herge as a young man I looked up out of curiosity:
https://fr.wiktionary.org/wiki/Herg%C3%A9#/media/Fichier:Gal...
Does he resemble Tintin to you? I would say he totally does.