This was a design decision we made, in order to keep all ExamDiff Pro settings under one key. Your logic is fine but it's just what we decided to do.But finding defaults stored, or not, in specific users' HKCU keys feels odd. I would have expected if defaults were to be stored in the registry that they would be in an HKLM set of keys, so accessible to all users. It's fine that individual users' settings are in HKCU.
ExamDiff Pro installer uses Inno Setup engine, so the directories it creates are beyond our control.I also noted that there appear to be four empty appdata folders, all created on the install date. They are
"C:\Users\<adminid>\AppData\Local\PrestoSoft\ExamDiff Pro "
"C:\Users\<adminid>\AppData\Local\PrestoSoft\ExamDiff Pro 9.0"
"C:\Users\<dailyid>\AppData\Local\PrestoSoft\ExamDiff Pro "
"C:\Users\<dailyid>\AppData\Local\PrestoSoft\ExamDiff Pro 9.0"
ExamDiff Pro itself only uses versioned directory name, for the user account it's running under.