Code is already there to show the reason on /ns info
if (na->nc->flags & NI_SUSPENDED) {
if (na->last_quit) {
notice_lang(s_NickServ, u, NICK_INFO_SUSPENDED,
na->last_quit);
} else {
notice_lang(s_NickServ, u,
NICK_INFO_SUSPENDED_NO_REASON);
}
}
As long as the struct still holds the reason it will display it