Checking the later pictures that you talk about, the alt text is found indeed. My recommendation though would be to give a summary of the data and not the conclusion. E.g. Gemini flash has error rate of x% while the others are y% and z%.

Maybe something is lost in the translation, but here it is what my screen reader makes out of the article:

Along the way we realized some of our math courses had not been updated in quite some time, and some schools were still leveraging these courses to teach. Images for equations are bad m’kay

It was immediately apparent was the use of images to represent equations like this: https%3A%2F%2Fsubstack-post-me… https%3A%2F%2Fsubstack-post-me… This is not great… the font is a bit on the smaller side and the font itself is not very legible, in my non-font expert opinion. Making matters worse, there is no alt-text provided that can explain the equation.

3 out of 5 images on the post have empty alt text (alt=""). most substacks are pretty careless about alt text and so previous poster is just noting that your accessibility post follows this trend. (It's worth noting the post you made previous to this has 0 out of 4 images with alt text.)

looking through it the images that are definitely content controlled by the user has alt text - that is to say the graphs, the first alt text = "" is inside a bit of content that is display:none and thus not available to a screen reader - I suppose the others, so it is not knowable if that alt text will be filled when the area is rendered (probably not) I didn't look for the other one but I expect it is the same situation because all the images I encountered that were in the writer's control had alt text.

About the empty ones I have not investigated but there are numerous situations in which an empty alt text makes perfect sense and is a better accessibility solution for most users of screen readers than otherwise. For example if they are inside something clickable that has an aria label on it telling you how to use that part of the dom, the alt text on a child image just makes things overly verbose and annoying in most circumstances.

I have an article in the works that touches on these issues with proposed solutions but unfortunately it would be too big to talk all about here.

on edit: of course it is possible that, being alerted to the fact, the writer has added the alt text in.