We set T133711: Question mark in query causes it to turn up unrelated search results as a subtask of this, because after that one is done, we will have a better idea how to handle question marks in this case.

I believe that there's some code somewhere that checks to see if a search contains special syntax (for some definition of special syntax), and if it does, then it does not display the "Create this page" suggestion because seeing something like "You may create hastemplate:fa" would probably not be useful. Since ? is presently special syntax, I suspect that's why this is happening.

While I think handling a question mark as special character is unfortunate (presumably borrowed from SQL or glob but very few users would be familiar with that), the fundamental problem IMO is our horrible article creation workflow. It makes sense to prompt for article creation after search, but that should not be the primary means of starting articles that is relied on by many power users (on huwiki which has a fairly small editor community we now get a report about this every couple days). That's apparently tracked in T29311: Add a "create a page" interface to MediaWiki core.

I just checked this on 6 random wikipedias, and it's working. Here's a link to see it on enwiki.