npub14xcjt6lvsws42s8yx5d4w9yrueecujj207vczy432j6dldq8pddst9zqkc (npub14xc…zqkc) npub145f0z7eue0rtgxezv76l972lrzk7s9u5ls5748jtkrg70v5lng9qp3wy0d (npub145f…wy0d)
Currently the only formal proposal is FEP-e232. It allows multiple quotes and uses only standard Link type from ActivityStreams, but it is not widely implemented.
The de-facto standard is quoteUrl property.
_misskey_quote may be recognized by some servers but not all.