Are there controls regarding good manners? And are good manners known through evidence, or is everything considered good accepted as such?

Sharia-based manners and customary manners have their own rules. The reference for Sharia-based manners is evidence from the Quran and Sunnah, while the reference for customary manners is the prevailing custom of people. Sharia-based manners are divided into recommended and obligatory, and their details are found in the books of the فقهاء (jurists). Disagreements concerning manners are referred to the Sharia if the manner is Sharia-based, and to custom if it is customary, provided that the custom does not contradict the Sharia. There is no evidence to support the idea that walking barefoot in Makkah and Madinah is a specific manner of showing respect to the Prophet (peace be upon him).