> Taking into account the purposes of the processing, the data subject shall have the right to have incomplete personal data completed, including by means of providing a supplementary statement.

You can just put a note on the account: "Actual name contains accent acute over second e of first name: our system is unable to render this. User is quite sensitive about this so apologize again for our inability."

Not every organization would require this, it depends on the processing. A bank would since it sends you a bunch of correspondence. A restaurant taking a reservation wouldn't if they wouldn't save and sell the information or use it for marketing.