Public decorum according to Halacha-Performing appalling acts in front of other people:[1]

[It is forbidden to perform an appalling act in front of another person, and one who does so will in the future be brought to judgment over it], as the verse in the end of Koheles[2] states “[Ki Es Kol Maaseh HaElokim] Yavi BiMishpat Al Kol Nelam/God will bring to judgment on all concealed matters.”

Examples:

1. Killing lice in front of another person.[3]
2. Spitting in front of another person.[4]
3. Spitting on the ground and leaving it in view of people.[5]

Other examples:

Anything which the general public in one’s current society is particular against doing in public due to it being improper or nauseating or disgusting, falls under the above law and must be abided by according to Halacha. Furthermore, even if there are only a minute number of people who are bothered by a certain action, one should avoid doing this action in front of them if one knows that it bothers or nauseates them, and certainly if he is asked not to do so due to that it bothers them.

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[1] Admur 156:15 “The verse in the end of Koheles states “[Ki Es Kol Maaseh HaElokim] Yavi BiMishpat Al Kol Nelam” This comes to include even one who kills lice in front of his friend”; M”A 156:2; Chagiga 5a; Kaf Hachaim 156:14

[2] Koheles 12:14

[3] Admur 156:15; Rav Chagiga 5a

[4] Shmuel Chagiga 5a

[5] Ketzos Hashulchan 146:30 footnote 13