Understanding Employment Contracts and Resignation
Basically, employment is a contract and it remains in force only as long as the parties are willing. As such, either of the parties can terminate the contract by strictly observing the specific terms of the contract, if any, relating to its foreclosure or exit. Resignation is the mode of terminating the employment contract at the option of the employee as a party to it. Therefore, it is the independent decision of the employee based on their own discretion.
Conditions for Accepting Resignation
When the resignation is in writing, conforms to the conditions of exit, and complies with the organizational protocol of communication, and no disciplinary action for any misconduct is pending against the resignee, the employer has no choice other than accepting the resignation. When the resignation meets all the above aspects, I don't think that the employer can have the prerogative, if any, to take exception to the reasons for resignation mentioned by the employee and refuse to accept it on that score and direct the employee formally to change the reasons. If the employer has any discomfiture about the reasons cited, why not try to take some remedial measures, counsel the employee personally, and request them to stay on? In the absence of any such positive gestures, it would automatically imply that the resignation is acceptable to the employer but for the reasons. No other individual, whether it be an organization or an employer, has the right to ask any other individual to change the reasoning for a lawful decision taken by them.
Moving Forward After Resignation
The poster can simply walk away if their resignation is in order in all respects without waiting for a formal acceptance. After all, their skills and experience are going to accompany them always in the future, if not a positive reference from such an adamant employer.