I grew tired of switching back and forth between admin and my user account, and only logged in as user. Set everything until it was right. Double-checked twice with Ctrl-Reload that settings look permanent and will not change upon force reload. Then logged out and in again:
Settings have magically reverted and STAY reverted, even after numerous Ctrl-Reload, so it is not "just" a caching issue. Something weird.
Another user setting that constantly gets reverted is "user accepts messages from others".