Add a persona who uses a public computer
[The commenter] then said, "this could be a problem in a public computer, when many persons want to use same account." It sounds like a kiosk or an Internet café. That is an interesting new persona to study, Community Team!! (to Gus, et al.) Usually though, public computers are configured for a guest account and/or to automatically log out after a period of time and delete the guest account's files.
It could be any shared device. A neighbor's laptop, phone, etc. If the device is public, then it isn't managed by a neighbor but by an administrator.
I guess this issue should be moved to tpo/ux/research. I wrote it in tpo/web/community because cypherpunks such as myself are not allowed to post in ux/research.