Well in this case as ping6 ff02::1%interface is a supercommon practice accross
ipv6 folks they should fix this, moreover this can be a simptom of broken
ICMPv6 in batman.adv networks, and in IPv6 unlikely IPv4 if you break ICMPv6
you broke the whole stack ;)
So David I encourage you to send a report on batman-adv ML and keep us
informed ;)
Cheers!