With good typography, the color of text blocks is even and flowing, and logical structure of headings, captions, block quotations, etc. is obvious and clear without calling attention to itself. With shitty typography, the eye is constantly pulled away from a regular flow by the uneven color within text blocks or by distracting elements on the page, certain words or phrases are illegible and require scrutiny (in some cases, switching focus back and forth between two places on the page or even between pages) and effort to figure out, and inconsistencies impose a small but continuous mental tax on the reader.
I'm certainly not, and I've never given two thoughts about typography except when weird things happen with it.
Sounds like he spends a lot of time reading, and it's natural for minor annoyances to become like Chinese water torture when one does something often.
As for full justification, I don't really mind it. It's not a pain point for me. If I wanted to be picky, I could come up with a list of minor issues.
The problem is the Kindle is the best reader out of a category of really shitty products.
I've started seriously contemplating going entirely to scanned, pirated PDFs and simply mailing the author a check the retail cost of the book. I'd love for technical books to start rendering PDFs for multiple common ereader screen sizes. Journal articles are too much to hope for.
Google Play Books supports having both EPUB and PDF for the same document, and, I believe, chooses between them based on screen size or other platform features. I don't think it supports having prerendered pages for different layouts yet, but certainly the "buy a title, which might have multiple formats for different devices" thing is already established there, so its not a big jump to see it being done with more specificity.