A favourite: if you opened an email attachement, outlook would silently save it in an obscure system folder, and never ask you to move it.
A colleague had worked for a w on it, and the deadline was that evening, but they couldn't find the file anymore.
I knew this should have been better.

Hi, no worries. We all have to learn at some point… I wasn’t aware of how visuals could have such impact either until it started hitting me a few years ago…