I pushed an update.
- Callouts are now rendered in history revision. Thanks for the suggestion @Noble_Fish. It might need ajustements, like not rendered in some situations. The collapse toggle is ignored and not rendered. Let me know how it plays on your side!
- Onebox excerpt should strip the callout marker. Works in RTE too. Let me know if you see other cases @nathank.
- Shortcut changed to ctrl/⌘ + alt + c. Great catch @scavin. It should be a safe change.