Mark as 'wontfix' and close. If they reopen, ban them, with a comment explaining why if you want ("I'm banning you because your feature requests are not welcome

Mark as 'wontfix' and close. If they reopen, ban them, with a comment explaining why if you want ("I'm banning you because your feature requests are not welcome"). It's really important to communicate that you are distressed. Remember, it's quite likely they think they are not causing any distress, and probably would prefer to know than cause any additional harm. Banning them accomplishes this. It also has the additional benefit that if the person is not being conscientious, they no longer can annoy you.