Spelling varies widely across the eras our ebooks were published in. Therefore we attempt to standardize spelling to what a modern reader might be familiar with. We only make sound-alike changes, like to-morrow -> tomorrow.
This is a common practice that editors and publishers have quietly engaged in for centuries. For example, today you are not reading Shakespeare in the way it was spelled in its first printing.
After reading this comment I couldn't help but picture medieval monks, toiling away copying old manuscripts into "modern" English. Normally a thankless task, so thank you!
Is there epub-specific html markup you could add to changed words to indicate their original spelling? Like alt text for images, but in a span around a word? There's the html "title" attribute, of course, which would work (mouseover shows the title attribute's value), but that isn't semantically correct for the purpose.
This is a common practice that editors and publishers have quietly engaged in for centuries. For example, today you are not reading Shakespeare in the way it was spelled in its first printing.