Should work like all other privacy settings. The first time the app tries to access the clipboard, the OS should prompt “Reddit is trying to access the clipboard [Allow / Deny]”. Then the preference is set and can be changed in settings.
They have this for certain things. MyFitnessPal asks me incessantly to have access to my "step" permission. I vehemently agree we should have more access to fine-grain permissions. Although apps should be punished for nagging me to change my settings every time I open the app.