Forget mobile, that's secondary. And it's not about the 100% thing you keep repeating, we're all browsing in incognito which retains no memory of web page zoom, if that was even a thing.
That medium.com article you shared looks shit too. But I can live with that for an article-based site. This is a post-based and comment-based site. Like reddit or 4chan. The earlier font you had was just fine. If people cannot read it, they should get their eyes checked or zoom beyond 100%. It would've been okay to increase the font size by 1 or 2 points, but not double it - this is messed up now.
This website certainly has scope for improvement, but font and button size is not one of them. We need better post management (so good posts don't get lost), better login and access, better html markup for comments to support media, etc.
Appreciate your hard work, and happy to help any way we can. But for now, the site's styling is total fucked up. Please roll it back.