I think a debate of installing/not installing to app data is drifting off topic. it is well covered elsewhere e.g. here.
http://stackoverflow.com/questions/1...les-vs-appdata
it came up here only because some one suggested a possible link between where it installs and whether it needs to ask a users permission to update.
maybe a shared Pc has multiple appdata installs of K for PC for multiple users, and even different versions co-existing ? dunno & don't much care as I am single user.
at one time I think I had two or more older versions left behind in multiple locations, I recall having to clear them all out when I was having sync & download issues
for most Kindle users, all that really matter is " where does it put the books" : answer: in My documents and each user has their own copy of that folder.