A real closed question (for example, this one) would have in addition a banner explaining who closed it and what is the closure reason. I guess the only damage that can really be caused by this is for fake-closed questions to receive fewer views.

That looks quite odd --- I never thought about this possibility. I think this trick is worth noticing. Do you think it could be exploited by someone with malicious intents? You can only use it on your own questions unless you have high reputation, and in any case it is easy to detect automatically and leaves permanent track in the database; so the answer seems to be "no". But maybe my "black hat" mind isn't twisted enough.