If during a conflict I use the oni mask on the Marauding oni to blank his text box then dishonor him.

What happens at the end of the conflict?

Marauding oni can't be dishonoured but he already is?

"Cannot be dishonored" prevents the act of being dishonored, which is different to "Cannot become dishonored" which prevents entering the dishonored status.

Thus, the Oni will remain in the dishonored status.

2 hours ago, Bayushi Shunsuke said:

"Cannot be dishonored" prevents the act of being dishonored, which is different to "Cannot become dishonored" which prevents entering the dishonored status.

Thus, the Oni will remain in the dishonored status.

Either way, he will retain his status at the end of the conflict. However, he will be unable change his status again after the Oni mask wears off. His wording prevents him from changing states. not from being in the state.

For example, playing Steward of Law into a conflict with someone already dishonored doesn't clear the dishonored status.