Loud talking in a theater, and such

• They're highly frowned upon
• Warnings to children
• Verboten verbiage
• Etiquette subjects
• Taboos (and title of this puzzle)
• List from an etiquette expert
• They're off-limits
• Forbidden items (hyph.)
• Prohibited things: Hyph

Wiktionary Word definitions in Wiktionary
n. (plural of nono English)