I am sure theDucks or dwanthny will fill in the blanks when they see this
. I can remember Kovid saying that due to a limitation in the mobi format he was unable to detect certain things which meant certain other things happened when you do it (maybe it was duplicated TOCs at the end or summary pages at the start or something). I didn't pay close attention because it isn't something I would ever do. If you are happy with the results then clearly it isn't too major or frequent.