How can the Hadith, "Whoever introduces a good practice (Sunnah Hasanah) will have its reward and the reward of whoever acts upon it," be applied when facing accusations of Bid'ah (innovation)?

The meaning of the hadith "Whoever institutes a good practice (sunnah hasanah) in Islam" is that whoever originates an action that falls under what the Sharia has commanded and encouraged, and for which there was no existing precedent during the time of the Prophet, peace and blessings be upon him, will receive its reward and the reward of those who act upon it after him. Examples of this include Umar's gathering of the people for Tarawih prayers and the Companions' compilation of the Quran. However, if the action falls outside of what is legislated, it is a reprehensible innovation (bid'ah sayyi'ah), and its perpetrator bears its sin and the sin of those who act upon it after him.