Hot take: CW, UI, UX, OATSS
Writing Content Warnings should be opt-out instead of opt-in.
Long form: Instead of clicking a button to make the CW field appear, fediverse clients should have an always shown CW field and refuse to post unless there's text there OR a button is pressed to signal "I want no CW".
(OATSS: Other Acronyms To Sound Smart)