[ElMiko]

Okay, but, since font size can theoretically be scaled infinitely, this goes to my initial question. What font size/screen size ranges are you assuming when determining your formatting parameters. What's the smallest screen at the largest font size that you're using as the idealized constraint on how you format books?

Just to give a little context here by way of example, in other threads I've asked about creating column-like formatting that will be preserved under "stressed" conditions. e.g. transcript-like text where the speaker's name is on the right and their speech is on the left. My default has long-been to use table formatting, but users like RbnJrg have also exposed me to span/float combos that will have similar effects. However, there are unavoidable combinations of font size/screen size that make it impossible to guarantee that the formatting will be effectively preserved. As you noted, that's just the nature of the reflowable beast. Therefore, an ebook producer has to ultimately make SOME assumptions about likely user settings and accept that SOME outlier cases will result in losses to formatting fidelity. The question is, therefore: What are the idealized assumptions that ebook producers are making to dermine the boundaries of what constitutes and outlier?