Nobody said they'll be injecting anything in their apps, where did you read that?
I know a bit about how Stellar works, and I can't imagine any kind of software they could "inject" in their apps besides perhaps a way to post a Stellar address into the current merkle-tree they host and a way to fetch that through an API. How is that worse than having a Bitcoin address optionally includable in the same way?
"All while integrating certain Stellar features directly into Keybase's apps."
The rest of their announcement, I legit don't care about. This is the deal-breaker here. You don't need a Big Announcement or to hire more people to add a Stellar address for verification. I know a bit about Stellar as well (granted, you probably know more) but this reads to me as a let's-be-a-wallet game.
And this is worse than having Bitcoin addresses: active functionality versus passive functionality. Difference of kind, yeah?
I know a bit about how Stellar works, and I can't imagine any kind of software they could "inject" in their apps besides perhaps a way to post a Stellar address into the current merkle-tree they host and a way to fetch that through an API. How is that worse than having a Bitcoin address optionally includable in the same way?