edit:
To make it clear to people not reading the comment carefully, I'm not saying MacOS is "free". I'm merely saying that once you pay for the computer, the OS is included in the price.
And there is no additional monetization under the form of ads or tracking. Unlike in the Windows world, where you pay for the license, yet you are still being tracked and served ads.
Where do I have to click to get those ads?
And anyway, surely that is a game, not an ad?
I'd go as far to say it is adware.
https://duckduckgo.com/?q=Candy+Crush+Soda+Saga+windows+10+b...
Probably it was this
https://gist.github.com/matthewjberger/2f4295887d6cb5738fa34...
You are misinterpreting the parent's argument by saying "it's pretty fair" then, as they were saying it's unfair to call MacOS "free."
In one case it just also happens to be impossible to avoid being further monetized via ads and tracking.
This, to me, is unacceptable for paid software, as essentially amounts to license fee + adware model.
The comment you replied to was a response to calling MacOS free, and was entirely about that topic. It's not a fair comparison to call MacOS free, that isn't justifying Microsoft's actions though.