How can one differentiate between blameworthy innovations (bidʻah) and good practices (sunan ḥasanah), and is what is stated in the noble Ḥadīth about instituting good practices and being rewarded for them correct?

There have been several fatwas issued previously clarifying the meaning of "Sunnah Hasanah" (good practice) and the difference between it and "Bid'ah" (innovation), and stating that there is no such thing as a "good innovation" in Islamic law.