Feature summary:
InpuBox is great for creating pages and other things.
But in my experience, it is confusing for the users why a search box would work differently - espacially the autocomplete.
Benefits
Users would get the same experience regarding autocompletion if they use inputbox (e. g. presented on a page) or if they type in the regular MW search box.
This has been discussed here also: https://www.mediawiki.org/wiki/Topic:Urwm08465wtkzk5c
Sharing what I posted in that other topic. Interestingly, we have autocomplete working in our front page InputBoxes on LIMSwiki.org. However, the problem we're encountering is even when we tell InputBox to limit the search to a specific namespace, the autocomplete does not also limit its suggestions to that specific namespace. I found an old inactive extension (Extension:FormInputMik) that advertises "autocomplete is provided on predefined namespace," which is exactly what we're looking for, but the extension is soooo old. We very much would like to see any autocomplete on an InputBox with namespaces="foo" limit autocomplete specifically to "foo."