SO if you want to disable the link i cant find it either but you can adjust how many they create as it wont allow them to create an account if you set it to a limit other than zero example 1 but this will also stop them from creating orginaization if you are allowing them to do that also.

so what i recommend is going here studio/navigation/system/Add Profiles and disable Person by sliding the slider to off doing this will stop them from creating additional profiles but still allow them to create organizations

Hope this helps

Bret.