Raising awareness of relevant products/services in a space with very few products/services is a good thing, I reckon. I don't think it matters that he's from Heroku or what his role there is, as long as the comment is relevant. Heroku is one of the closest competitors to App Engine. This is relevant, as both relate to Go support. It's also not as though he went through every comment thread here mentioning it; it was just one comment.

I think you'd be right if he did it in some kind of obnoxious way, but he didn't.