One fediverse enhancement proposal (FEP), FEP-e232, proposes a way to represent inline quotes and other text-based links to ActivityPub in a manner similar to mentions on other social media platforms. Another method would be to use the quoteURL property within ActivityPub, which would assign posts an ID that could then be pulled into other posts that want to quote them. Misskey created its own solution with its _misskey_quote property, which builds on FEP-e232.