Dear Micha,
when you change target type to
File with the same layout and open the file in an editor, you can see that there is simply no username present in the messages. That's why the username can not be displayed in Log4View.
It seems like NLog does not support logging the username when using the log4jxmlevent format. Yet solution aproaches are discussed
here.
Yours sincerely
Philipp Lauchner
PROSA GmbH Development & Support