ActivityPub even has the mechanics to facilitate it through publishing Person records. There is MASSIVE space for innovation, especially if you prioritize on non-monogamy, non-heterosexual, non-gender-conforming needs.
Dating apps are a REALLY hard space to get into, however. You need a cumulative mass of users in a given area before they’re useful, and monetizing it inevitably means making the app less useful. There’s a reason okcupid went to shit after it stopped being a non-profit.
And then there’s the moderation problem…
How you'd envision it to work, considering the open nature of ActivityPub but the need/want from the users to remain private when using dating applications/protocols?
For messaging, I hadn’t put a much thought into it, but one could establish end to end encryption based on mutual validation signatures. Theoretically. Encryption isn’t my strong suit, but as long as the encoded body is unicode, it’s just as easy to transmit as any other text.
But, like, I also don’t know of any dating site that professes to be encrypting message contents.