ETA: Added one of the threads on the KDP authors forum: https://kdp.amazon.com/community/thread.jspa?threadID=281868&start=0&tstart=0
Good Ereader is not the most reliable source, but word on the author forums is they've already started sending out the mails saying the book will get a public warning unless the problems are fixed. They've always sent mails about this stuff, they just didn't pull books off sale unless the book was deemed "unreadable" and they never warned on the actual *sales* page.
Looks like only verified purchasers with specific Kindle devices reports for spelling will be taken into account. AFAIK, once more than a few errors for the same item are reported, it's investigated by actual human eyes, and the author does have a chance to defend their position if it's an intentional misspelling (so "No that's British English" shouldn't be an issue).
This might be a little interesting. Of course, Trad pub doesn't use KDP, so it won't affect them unfortunately (some of the absolutely worst formatted and full of OCR errored books I've ever got were trade pub rescans of out of print pre-digital books. Even the very worst of the self-pub doesn't approach the kind of mess that can make!)