Internally, MediaWiki treats temporary user creation on edit as an autocreation, ie. the $autocreated flag of LocalUserCreated will be true. Various extensions use that flag to differentiate between a new user and existing user (who is getting a new account because they are visiting a new wiki, on a wikifarm with a central login method such as CentralAuth); this will not work for temporary users. This seems like it could become a problem, e.g. for actions like onboarding messaging which we want to run only once per user and not every time they visit another wiki.