How do you turn on/off AppxDSvc logging?

You can adjust the logging parameters by setting three registry values:

LogServiceDir - set to the name of a directory and AppxDSvc will write the log there (in a file named $(LogServiceDir)\serviceName.log

LogAllEvents - set to 'Y' to get a complete log or any other value to disable most log messages. The default is 'N' so Jean should be seeing very few message written to the log

LogCreate - set to 'Y' to create a log file or any other value to disable logging. The default is 'N' (starting with 4.2.3 - it defaulted to 'Y' before release 4.2.3)