A couple years back, I was surprised when my Arabic teacher, who is a hardcore Salafi, would always say Imam 'Ali ('alayhi al-salam), but if you look at the books of early scholars, you'll see that it is not uncommon at all for them to say 'alayhi al-salam after the names of Ahl al-Bayt. Open up al-Maktabah al-Shamilah, go to the search feature, go to the "kutub al-mutun" section, select all the books, and search for "علي عليه السلام." You will be surprised at how many muhaddithin say عليه السلام after mentioning his name. Not sure why it has come to be a distinguish feature of the shi'as in our time...