I like being able to choose between pages and percentages; maybe there could be a third option added, “Kindle” pages or bookwalker / ebook pages? I know you can edit the page numbers, but I don’t want to change the page numbers to 2000 when it’s a 500 page book and have crazy “has read pages 1500-1800” activity updates. I also want to keep the reading speed graph data accurate and comparable across books. I want to keep the “pages read” data true to the actual paperback count, but I want to enter the kindle page number I’m currently on.
I am a bit unhappy with how all of this is currently being handled, but I’m afraid it will take some time until we get to a point where we can change this. We first need to revamp the whole site or else we will introduce many conflicts between the old and the new parts, so I need to ask for some patience still 
It seems very common for Japanese learners in particular to use character counts rather than pages/percentages to be more accurate. Maybe that’s something that could be considered for a tracking metric, too.
In particular, ttsu gives you the character count (as well as the percentage calculated from that), so in some ways it’s easier to use character count when reading there.
I feel like the newest fork of Mokuro also can track with characters, but I’m on a super old timey fork so this is only hearsay for me 
