xi-editor does use xi-rope as its main text storage data structure. This part worked well; the problems with xi were much more around the CRDT and the fully async design. I did a RustLab talk on the use of immutable data structures (of which rope is a good example) for incremental UI, and this will be published soonish.
Yeah I remember thinking the async design seemed a bit over-engineered. It seemed like they were approaching the UI constraints almost like they were developing a game engine, which doesn't seem needed for a text editor. For a great many actions, in that setting it's acceptable to have synchronous actions between key press and view update.
