Setting syslogd_flags="" or syslogd_flags="<value>" in /etc/rc.conf is ignored on boot and instead you get the default flag value "-s" as defined in /etc/defaults/rc.conf. Other init scripts that I tested behave as expected and honor their _flags in /etc/rc.conf
Killing syslogd process "killall -9 syslogd" and restarting with "/etc/rc.d/syslogd start" set flags as expected
I also noted that there is no DEBUG output in /var/messages for syslogd on boot when rc_debug="YES" is defined in /etc/rc.conf
FreeBSD charon 10.1-BETA1 FreeBSD 10.1-BETA1
Updated 10.1-BETA and 10.1-RC versioned bugs to 10.1-STABLE.
I am unsure when this was resolved, but I cannot reproduce this behavior.
Thank you for the report.