Ads and marketing in general aren't binary. It's just that the ones that are only trying to grab your attention or build brand awareness tend to be on the more intentional and less helpful end of the spectrum of reputation signals.

Things we like to label "good marketing" tend to be more towards the middle of the spectrum by sharing useful information as a way to build reputation. On the opposite end of the spectrum from ads would be word of mouth, like that coworker who everyone loves for their competence.

Well, you could convince me I suppose ! Since I don't think ads are inherently bad, it doesn't bother me though. The line between information and "decent" advertising is quite blurry in my opinion anyway. (Decent meaning roughly "we merely want to inform you our product exist and we hope you'll maybe like it")

Abstract it this way and it’s hard to argue that any blog post (or stack overflow answer or, I suppose HN comment) isn’t an ad. Or conversation at a cocktail party, for that matter (“lapetitejort seems to know a lot about bikes. I should ask them about mine.”)

I'm fairly sure most people wouldn't put intentionally getting fired in order to sue an employer in an advertisement for their services.