I was told here that not using diacritics (specifically the cedilla) is bad usage for those who know — I assume — their diacritics.
Is that correct?
Is garcon a correct spelling, in English, of the French loanword garçon? That is, is it valid to drop the cedilla?
In general, what do style guides and other authoritative sources say about using diacritics in English? Are there contexts — again, in established English words, loanwords or otherwise, not in quoting foreign texts or proper nouns — where:
- the consensus among authorities is that diacritics must be used?
- diacritics were once used, but are no longer in widespread use, even by professional typographers¹?
- diacritics once in widespread use are actively discouraged today?
What is the general disposition of diacritics in modern English in professional writing and typesetting, taking into account prestigious sources in both print and online?
I'm more interested in proper orthography than in effective typography, but I'd appreciate perspectives from both fields².
I would like answers from a range of authoritative sources, like style guides (Chicago, AP, etc) or house styles (The New Yorker, The Atlantic, The New York Times, etc).
¹ For example, coöperation, belovèd of The New Yorker?
² Bonus points: what about ligatures? When debating this topic with my friends, should I cavil about diaeresis or diæresis?