Why is it that charts and especially maps are especially hard to view on a Kindle? Unlike the font size on a page, they can't be enlarged. I had to break out a magnifying glass in order to read some (not all) of the detail in a recent book. Good thing I had my laptop with me in order to get an idea of the surrounding islands being described in the book.
Yeah, I guess I *could* have tried using the "Experimental Browser" built in to Paperwhites, but for the most part I only use it (the browser) for dictionary definitions that the default one doesn't include.
however, you can enlarge images on e-ink kindles by log pressing on the image and then tapping on the magnifying glass and pinching out as needed. Unfortunately the resolution of images is entirely up to the publisher and they often use too low a dpi on images resulting in fuzzy images and unreadable text when you zoom in.
I would suggest that you do three things when you run across that problem:
1. use the Feedback Box at the bottom of the product page on the Amazon website and indicate that there is a formatting problem - Amazon will send this on to the publisher and they might correct it
2. write a review of the book and mentioning the problem. Reviews of books on Amazon are not book reviews, but are product reviews
I've tried the steps you described, all yielded the same unsatisfactory results and am of a similar opinion that it remains a detail that most publishers don't place much, if any, importance on.
The issue isn't one which I encounter with most books I read on my Paperwhite; they are for the most part exclusively text only. I've considered using the Feedback/review steps you recommended, but there's a lingering cynical suspicion that it will be of little use or result.
The review is, in my opinion, the one most likely to get results as a bad review could reduce sales of the book. Also, after a lot of people complained, one book that had unreadable charts was pulled from the Kindle Store