I noticed that MDN has two pages for localStorage, where I think there should be only one. The pages are:
Probably any unique info on the latter page should be moved onto the former? And then “Storage/LocalStorage” should be deleted?
So, the problem here is that the page currently at API/Storage/LocalStorage should be at API/LocalStorage, which is currently a redirect to Window.localStorage.
Window.localStorage is an instance of the LocalStorage interface, so both pages should exist. I’m fixing it right now.
Except that there’s no such thing as a LocalStorage interface in the spec:
Yeah, I realized that after starting to make the changes and reverted them, but cleaned up some text and whatnot to hopefully clarify the situation a bit. Also retitled the “LocalStorage” page to something that doesn’t look like an interface name. 
I’ve also moved the page to Web/API/Web_Storage_API/Local_storage and added the Guide tag, since it’s now more of a guide: