It seems syslogd will send messages to all uses via 'wall' if '*' is used as a destination in the /etc/syslogd.conf file.
The default config has this line in it:
*.emerg *
Commenting this line out and reloading syslogd completely suppressed the messages, but you'd better remember to re-enable them later.
I did not find a way to supress them for just one session. The command 'mesg' should be able to stop incoming messages in a session, but it did not stop these messages.