If want to log full utf-8 strings “emoji’s” use the option -8, example on /etc/rc.conf:

syslogd_flags="-ssC8"

The optiosn are:

 -s      Operate in secure mode.  Do not log messages from remote
         machines.  If specified twice, no network socket will be opened
         at all, which also disables logging to remote machines.

 -C      Create log files that do not exist (permission is set to 0600).

 -8      Tells syslogd not to interfere with 8-bit data.  Normally syslogd
         will replace C1 control characters (ISO 8859 and Unicode
         characters) with their “M-x” equivalent.  Note, this option does
         not change the way syslogd alters control characters (see
         iscntrl(3)).  They will always be replaced with their “^x”
         equivalent.