When I Requested Amazon's Data on Me, I Didn't Expect What I Would Get Back
theguardian.com
theguardian.com
of course they are stored....
From what I read there might even be a toggle option for "annotation backups" in the devices settings.
I've a different worldview wherein I automatically assume that any online, phone or interactive activity that I engage in will be monitored and recorded automatically and I take steps to either not engage in them or I actively take steps to nuke the data collection.
I suggest: "Every highlight tracked on Amazons Kindle"