[Pajamaman]

I almost always only read very simply formatted books, and I am pretty insensitive to format etc as long as the book is readable.

I never use kepub. Should I?

I will add that converting to mobi and back to epub removes any device crashing gremlins. I have found that linux-based ereaders (Kobo and Sony) are vulnerable in a horrid ways to gremlins in epubs. I have seen massive battery drain due to certain epub, and db corruption. Convert to mobi fixes that. According to your words, I suppose conversion to kepub will also fix that.