Returning to Italy with valid visa & expired PdiS...?

Dear all,
I have been researching this topic extensively but have so far come up only with contradictory information; perhaps one of you would be willing/able to weigh in. I have a friend coming to visit me in Italy from Russia (with Russian citizenship) - he was a student in my university but graduated last semester - and he wants to make absolutely sure that he will not have problems to revisit the country for a couple of days. His type D multiple-entry visa is still valid, but his PdiS expired on February 2 (no plans to renew since he graduated). I have never heard of the visa being valid for longer than the permesso, so I cannot tell him with absolute certainty whether he will have issues at passport control. Any input would be most welcome! Grazie mille!

Hi ParliCaprese, I just came across your question, hopefully my reply is not too late.

I am an American and had a similar situation- a visa that expired after my permesso di soggiorno- and I did not have any problems coming and going into Italy during the period after my permesso expired.  I just showed my passport and visa at customs and did not show my expired permesso. 

When applying for a student visa in your home country, you have the option to choose up to 365 days maximum.  Then when in Italy, the Questura will issue the permesso only for the length of the school course.  I had a 365 day visa for a course that lasted only 9 months, so for 3 months I had a valid visa but an expired permesso.

But as I said, I had no problems coming and going.  Hopefully your friend from Russia will have the same experience.