What is the ruling on saying "Ali ibn Abi Talib, may God's prayers and peace be upon him"?

Ali ibn Abi Talib is, without dispute, one of the Ahl al-Bayt (People of the Household); indeed, he is the most virtuous among them after the Prophet Muhammad, may Allah’s prayers and peace be upon him. This is confirmed by the Hadith of the Cloak (Hadith al-Kisa'). As for invoking prayers upon him individually, scholars have differed on this matter: Malik and Shafi'i forbade it, while Ahmad permitted it, and the latter opinion is the more correct one. However, making invoking prayers upon Ali a distinct slogan associated with his name alone, thereby paralleling the Prophet, may Allah’s prayers and peace be upon him, is considered an innovation (bid'ah).