I believe packaged /etc/rsysog.d/50-default.conf contains a typo.
The following configuration block from /etc/rsysog.d/50-default.conf catches all user facility messages regardless of their priority:
Therefore all user facility messages are basically doubled in both /var/log/user.log and /var/log/messages.
Correct version of this filter should be the following:
This change fixes doubling of user facility messages, only user.info messages will end up in both /var/log/user.log and /var/log/messages.