It was just a friendly heads-up that the article was basically unreadable because whole words were getting cut off each line.

I don't see why it matters who runs medium in this case.

Medium is more or less a blogging platform. I don't think that people who post essays on there have much control over how it displays on any given device/browser, given the minimalist text editor it provides.

I would have imagined the choice of blogging platform is 100% controlled by the author?

I'd love to comment more on the actual blog post subject, but I can't read the article, so I figured giving a headsup would be of interest to the author. Next time I'll just shut up and move on, it's not my loss.

No, but she is using a theme she made herself (she links to it on her web site).

That makes more sense in terms of page layout and so on. Do medium themes let you control things like zooming behavior, though?

I haven't got a clue. But it was her choice to have a (pretty) background that made the text hard to read unless it was at the bottom of the photo.

If she could ruin the readability by choice, I would certainly expect her to ruin the zooming behaviour too if she could.