Earlier quoted context omitted.
surprised helix doesn't support the . key - is that incompatible with its interaction model somehow?
Yes, its model is that you make a selection and then act on it. After the action happens there's nothing selected. The editor can't infer your intent in making the selection, so there's no reasonable notion of repeating the last edit. You can separately repeat the last motion or last action, but not the whole edit---which of course isn't as useful. Helix would _ideally_ like you to tell it ahead-of-time everywhere yo…
But as an extremely heavy user of vim repeat and macros for the last two decades, it strikes me as a wee bit audacious to so completely dismiss its utility.