The comments about cross-wiki editing from T357499 apply here as well – I think we’ll have to be satisfied with the redirect just returning to the item that was created / edited, rather than to the wiki page where the user was using the link item widget. (If we get complaints about that, we can always work on it later.)

Per the investigation in T351971, the link-item widget only shows up for logged-in users. Users logged-in to a wiki supporting CentralAuth should also get logged into the repo, so it should not be the case that a TempUser can be created through the link-item widget. If a user tries to edit and is somehow not logged into the repo, they see this message:

On that basis, I agreed with @Lucas_Werkmeister_WMDE that we can move this out of T357020. As Lucas points out, there is also a ticket T140661 for adding support for the link-item widget for anonymous users. This task will then be a subtask of that - the implementer of T140661 must take care of the case that the edit creates tempuser and returns a redirect.