By 1925 etiquette books reduced public-space rules to avoiding conspicuousness

Evidence

Standard Etiquette, published in 1925, contains a general discussion of proper behavior in traveling and business but limits its explicit instructions to two pages of brief don’ts: Don’t talk in a loud voice or act in an eccentric manner, both make one conspicuous. — Lyn H. Lofland, World of Strangers_ Order and Action in…, 681

Categorization

• DEEPTHINKING: The endpoint of the excerpt series — public decorum’s whole residual rule is ‘don’t be conspicuous,’ the exact pressure that produces private, anonymous observers like Julius.