Quotation marks in any disguise name provide players with a visual cue that the name is actually false, automatically leading them to make some assumptions about another identity that their characters could never deduce and to treat the marked characters with undue suspicion.
Essentially, quotation marks signal that there is something to be discovered, encouraging metagaming behavior, especially in scenarios that involve many players, as some of them may not at all be motivated to consciously force themselves to believe in obvious deception.
Such information is usually exploited by involving other people to bypass the intended difficulty of a disguise, by re-rolling the spot checks until successful, an already overpowered ability common among good-aligned, wisdom-based characters, or by ignoring the disguise altogether through even more sophisticated means.
Knowing that disguises are marked discourages players from engaging in creative role-playing involving deception, as their efforts are guaranteed to be undermined, resulting in prematurely discarded or disrupted plots as well as derailed, potentially interesting narratives.