OK, this is my self-reminder to not edit mentions in Tweesecake. It seems to drop the domains of mentioned users, which causes a default to my instance, meaning all the mentions break spectacularly.
@app
@BorrisInABox @app it hides domains in posts for clarity of speech, I'd assume, but this then seems to follow through in the UI when composing or viewing. Weirdness.
@BorrisInABox @app I reported this months ago; it's pretty annoying and seems like the kind of thing that should be fixable.