I read it as stating that there was a curse, and everybody had noticed it, and acted accordingly (McGonagall trying to keep Quirrel through the entire year, Quirrel refusing to stay the next year.)
Ah! That makes more sense. I was reading it as "were there a curse, and everybody had noticed it, it would be god-damned fixed by now to avoid having to pay every DADA professor a zillion Galleons of danger money".
ETA: There is now a third thread, so send new comments there.
Since the first thread has exceeded 500 comments, it seems time for a new one, with Eliezer's just-posted Chapter 33 & 34 to kick things off.
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