Just confirmed this is the result of a change to the NM plugin. I'll go make appropriate corrections shortly.
Updated default lang_msg_sender and lang_msg_receiver to &c| &8[&6%sender_server%&8] &b%sender% &7> &8[&6%receiver_server%&8] &b%receiver%&7: &f%message% and &c| &8[&6%server-sender%&8] &b%sender% &7> &8[&6%server-receiver%&8] &b%receiver%&7: &f%message%. Make sure to update the placeholders you're currently using.