So on @chris1, regarding the backspace issue, I can’t reproduce this issue, you can check it here. I was testing on Mac via Chrome as you can see, and the undo feature works fine inside one module, but if you deleted the module you can’t step back from there, cause the logs are saved for each module separately.
I have only one idea why it may break, right now I was tested with Grammarly enabled and also have few issues, not with backspace but it may be not predicted scenario, cause Grammarly add some changes to the source code HTML, please disable Grammarly for demo page and try again to test Modular editor.
Hope it helps,
Thank you,
BR.
Nik.