Sharing dinners

"Uno per due". Works fine. Either they will split it for you (uncommon), or more likely they'll just bring an extra plate for you to split it.

This has been discussed before with no definite conclusion. The portions in Europe are much smaller than typical American portions. Two, you can always order alacarte of just a salad, etc. There is a general feeling that plate sharing in Europe is not as common as the US but American tourist do it all the time. And I have never seen a plate charge for a split plate that you often see in the US. You can do it but just be subtle.

We do not ask to split things. I just pass my plate to my husband when I have finished what I want, generally about half. It actually works really well for a light eater in Italy. We order a couple of antipasti and share those (ask the waiter to put them in the middle of the table.) Then my husband orders a pasta course, and I order from the "secondi" (meat or fish course). He eats all his pasta and half of my meat or fish, ending up with a 3-course meal, and I have a nice light meal with several selections. You won't want to do this 5 or 6 times a day though. You can buy panini, tramezzini, or other small snack sandwiches at a bar throughout the day, or yogurt or fruit at a grocery, etc. for your other light meals.

sharing is fine, I do it all the time
don't ask to split meal, just order what you want and pass plates around

I think you request an "uno for due".

Sharing is generally ok but be aware of several things in Italy: If two people order from different courses, you will not get them at the same time. So if one person orders an anti-pasta and another a main dish, the latter will sit and stare while the former eats their meal. You could request them served at the same time, but don't be surprised if they come separate anyway. Any sit down meal in Italy is a 1-2 hour affair almost without fail. Trying to eat several small meals a day will "eat" up a significant portion of your day. For intermediate snacks, stick with street vendors. Dinners (which start after 7:00) at nicer restuarants are expected to be a longer affair with several courses. Ordering just anti-pasta or appetizers or just sharing a main course would be considered rude. It also hurts the restaurant's business since they depend on few seatings with longer meals. So avoid such restaurants at night if all you want is a smaller snack. A pizzaria or informal restaurant would be a better choice.

Thank you everybody for your kind responses.

My wife and I have done it many times in Italy. Never had a problem with it.