Ok here's a weird one for ya:
I did not do any of the steps required to "Fix iMessage" when I did a fresh install of macOS Sierra on my hack, nor do I have a wireless card from osxwifi (thereby discounting the possibility of Handoff/Continuity). I wasn't really looking to add the feature. And now, about a week after the fresh install, the Messages app starts showing iMessage messages my wife is sending me?? I was unable to respond from the Messages app itself (they were flagged as "Not delivered" and now anything I send from Messages tries to use SMS and, I assume, Handoff/Continuity). Notwithstanding, the entire conversation, messages she sends me and messages I send her from my iPhone, is now showing up and updating in real time on Messages.
Anybody seen this behavior?
According to the Messages app, it is logged in using the iCloud account.
Weird...