The page stackoverflow.com/about still says questions may be closed.
Questions that need improvement may be closed until someone fixes them.
It would be better to say that questions may be put on hold until someone fixes them.
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I think the existing wording is the simplest way to convey the idea. The About page is aimed at new users or visitors who don't need to know or care about the intricacies of our closing process.
Just being introduced to the notion that questions may be closed (whatever that means in practice) is enough, and the actual mechanics, help pages, wording on the close reasons, et cetera can do the rest.
Questions that need improvement may be put on hold and, if not improved within five days, closed.
However, since sometimes a question may takes hours or even days to get closed, it may be useful to clarify whether "five days" is from the point of closure or from the point of asking.
As an aside, when checking to see if there is a functional difference between "on hold" and "closed" (which we may also want to clarify in the text above, because my suggestion makes it sound like "closed" is worse), aside from the friendlier wording, I found a typo in the FAQ. Yay me!