This NIP is not yet in main. Here is an overview of PRs referencing this NIP. 
Kind 16 generic reposts MERGED @fiatjaf
Update 18.md for reposting parameterized replaceable events CLOSED @digi-monkey
Implement Markdownlint GitHub action OPEN @mariano-perez-rodriguez
Markdown improvements, embelishments, and standardizations CLOSED @mariano-perez-rodriguez
Maybe bring back NIP-18 MERGED @arthurfranca
NIP18: Reposts MERGED @fiatjaf
private dm events OPEN @Giszmo