Many of the OperServ commands are listed in the OperServ help files however they are issued with different services agents such as NickServ or ChanServ, the reason why they are listed under OperServ is because you need OperServ access to issue these commands. OperServ access levels are Services Administrator also referred to as SA, ChanServ Super Op aka CSop, and root administrator.

WIPE - Delete all entries in a nick's memoserv ignore list

/os help memoserv wipe