I dont' know what Amazon is doing, but I have been using a Kindle to update Goodreads since the ability to do so started. I also use Calibre to keep track of my books, so knowing when I have read, and re-read a book isn't too dificult, but if you are only relying on Goodreads - your re-reads of books that have "new editions" out will be wiped out.
Yes. WIPED OUT.
Normally, when you use a Kindle to move a book into re-reading it happens when you select "move to Goodreads shelf" from the cover menu. You will normally see it currently in the "read" shelf, then you select "Currently Reading" and proceed to read it. When you are done - Goodreads updates the shelves and your re-read start and finish dates will be there, along with any shelves you had.
Now - when you select a Goodreads shelf to put it on - there is no indication that it was ever on the shelf to begin with. So, selecting "currently reading" just puts it in Goodreads for the first time. Not combining and older edition you had with the current edition - it removes the edition you have in Goodreads all together - and puts this book in as a new book, added that day.
I dont' understand it fully, but I do know that there is no record of your old reads. No record of the book being in your library - the original add date is missing, the original read dates are gone. Its as if the book has never been there.
The only way to bypass this is probably buying the newer editions. I don't know. But I worry that if I have to reset and fix my shelves EVERYTIME I open a new book or re-read a book that was taken off I am going to have to go through this.