Being the Italian section of SE I find it silly to force people to ask or reply in English. I find it a plus that there is the possibility to ask and receive answers in different languages. The ones that cant write a question in Italian would already use English anyways.

For replies I see its customary to use the same language as the question but I would specify it as courtesy rather than a rule and would like to see also replies in Italian.

Personally I would accept a question in any language provided they can attach at least an automated English version. It might help people that are not fluent in English and cant write in Italian to ask a question rather than shy away from the site. There's even the chance they might receive an useful answer directly in their native language.