Shulchan Aruch Siman 98:5 is seemingly talking about Ch'n'n by keilim.
Is it just talking about the bliot in the keilim, or the keilim themselves.
There is a three way machloket by Rishonim. The Rashba holds that if we stir a spoon in milk and then within 24 hours a k'zayit of meat, we say the bliot are Ch'n'n. The Ramban holds we do not say Ch'n'n by bliot. The Mordechai holds that the kli becomes Ch'n'n if we can't completely remove the issur by hagalah (so this only applies to Kli Cheres)
Rama says in Torat Chatat (quoted by Taz 8) that by milk and meat we are machmir that a kli cheres and its bliot both become Ch'n'n, and in a hefsed we don't say this by sha'ar issurim.
The Taz (8) holds like the Rama but is meikel by the kli with sha'ar issurim, but not the bliot. The Mishb'tzot Zahav says that in a hefsed the Taz would be meikel even by the bliot (the Gilyon Maharsha disagrees, and says he is meikel even without a hefsed).
The Shach (21) holds that it is only bliot that become Ch'n'n, and only by kli cheres in all situations, but we are meikel for other keilim in a hefsed merubeh. The Siftei Da'at holds that the Shach is only talking about milk and meat here, and would be meikel in a hefsed k'tzas for sha'ar issurim.
So I think what your friend was getting at is we don't hold by Ch'n'n by keilim, but there are certainly opinions that do.
Sefardim generally hold by the Mechaber who says only the bliot are Ch'n'n (by milk and meat - following stam opinion even in a hefsed merubeh). Ashkenazim hold by Shach since the Rashal, Bach and G'ra hold the same, i.e. keilim do not become Ch'n'n, but the bliot do (see above).