As documented at Keybase ♥'s Mastodon, and how to get your site on Keybase, lots of people are now using Keybase to securely engage with other people who they know via a variety of public profiles, from GitHub to Mastodon to Twitter and Facebook.
Stack Exchange should integrate with this system, so that if I want to securely communicate with or share private Git repositories with individuals or groups from the Stack Exchange community, we can securely authenticate with each other based on profiles here.
Update: Note that this has nothing to do with authentication for logging in to Stack Exchange itself. It is all about being able to authenticate in other contexts using your Stack Exchange identity. It wouldn't force anyone to use Keybase or subject anyone to any spam, but only allows them more assurance, if they choose to use it, about who they're interacting with.
Update 2: Also note that using this integration would be entirely optional and voluntary for each Stack Exchange user. It is just a way to verifiably associate yourself in other contexts with your SE reputation.
Update 3: Note that Stack Exchange is more than a network of sites with questions and answers. It is a network of communities. Many users are proud of their contributions here, and value the networks of associations they have formed both with others here, and with others outside SE. They want to be able to identify themselves with their contributions "in real life". This is a fundamental aspect of modern notions of identity itself, evidenced by the movement towards federated identity and user-centric identity.
Note that since users can already post text on their profiles here, supporting this integration makes linking identities more convenient, but doesn't fundamentally change the fact that there are already ways for users to add "proof" content to their profiles to demonstrate who they are on Keybase (and on PGP and via other cryptographic methods). Users are doing this already. It just makes it much clearer and easier for people to do so, strengthening ties and benefiting both them and the wider community.
Building reliable reputation networks like this is a crucial step in fighting fake news, fake identities, social engineering and security breaches in general, and giving the Internet a strong, robust and diversified foundation moving forward.
So I think this kind of support would help build the community, and thus Stack Exchange in general, though not directly help with questions and answers, nor fundamentally change what users can already do.