Is supplication after prayer, whether congregational or individual, considered an innovation (bid'ah)?

Scholars have differed regarding the meaning of "dubur as-salat" (end/rear of the prayer) in the Prophet's (peace be upon him) saying to Mu'adh: "Do not forget to say after every prayer: O Allah, help me to remember You, to give thanks to You, and to worship You in the best manner." Some scholars, and this is the view of the majority, said that it refers to supplication after finishing the prayer. Others, including Ibn Taymiyyah and Ibn al-Qayyim, said that it refers to the end of the prayer before the salutation (taslim). This latter view is strong for several reasons: the word "dubur" is generally used to mean a part of a thing, what was narrated from the Prophet (peace be upon him) after the prayer were adhkar (remembrances) and not du'a (supplication), and supplication within an act of worship is better. Therefore, it is preferable for a person to supplicate before giving the salutation from the prayer. He may also supplicate afterwards, but he should not do so habitually, unless he supplicates after the prescribed adhkar. Individual supplication after the prayer is not an innovation. However, communal supplication was not narrated from the Prophet (peace be upon him), nor from his caliphs, nor his companions, and it is rejected based on the Prophet's (peace be upon him) saying: "Whoever performs an action which is not in accordance with our matter (religion), it will be rejected."