: put their word into [?brackets] with a question mark [?it]?
This was adopted from S'pht terminals in M2 and Infinity, where it used to signify a questionable translation. The brackets and question mark are basically saying "I think this is the right word to use here, but I'm not entirely sure", "I" in the M2 terminals being whatever program is doing the translation, and "I" in common conversation being whoever is writing that. A similar way of writing is to suffix with a parenthetical question mark and no space, like this(?), which indicates the same thing ("I'm not sure this is the right word to use here"). A question mark separated with spaces (?) indicates that the whole preceding phrase (determined by the reader's own best judgement) is questionable.
