Since you apparently weren’t around for the rise of social media (ca. 2000-2020 C.E.), let me fill you in: user posts are content, too.
If you read more of the author's post:
> We are a webcomic duo that has been creating original comics since 2011 and sharing them on various platforms on the web
> Any business model that does not acknowledge this and does not seek proper compensation for artists is not of interest to us.
My point is, while I agree with their sentiment, I believe they are mistaken that artists are the core driver of social media growth. (And by their assertion, the reason people use social media.)
Regardless, users posting only life update-style text posts are also uncompensated for their contributions to the network (and their works too are feeding AI.)
But my point remains. I don't feel like I should be compensated for my HN posts. My great aunt doesn't expect compensation for posting her cat pictures. To be honest, I don't care about consuming artists' content. I'm sure it's great. But I go to the local art museum for that. When I go on social media, it's to hear from my great aunt.
And if YC wants to train a model that will eventually replace me, sure. I don't want to be paid for it. The whole thing is inevitable. You can't stop technology, only delay.
People just want to enjoy using computers (in the time humans have left).