Default setting for log file should be changed to Data\logs or something like that. Tools->Options, then scroll down to 'Log file'.
Edit: seems like that USERPROFILE\AppData\Local\qBittorrent\logs directory will disappear when the application exits and it gets saved to the Data directory. Must be a technical reason why it can't just stay in Data to begin with (so if qBittorrent crashes, it won't leave residue on the host computer.) But I can live with that. You can delete this thread.
Somewhat related... The way it works right now, all of qBittorrent's settings are stored in an INI file which is moved (not copied) to %USERPROFILE%\AppData upon startup. These are moved back once qBittorrent exits. However, in the the case of a system crash or power outage, this directory could be left on the host computer and, worse yet, you would lose your settings.
Shutdown computer, forgot to exit qBittorrent. qBittorrent tried to recover. Lost everything in LocalAppData_qBittorrent, but AppData_qBittorrent seems OK. Odd.