@2 Actually right now this is the default behavior. Converting bolck elements (h1-h6, pre, p) always changes the whole block and does not split the selection. This could be changed in future.
I used the Try It page. It does support undo of markup when you do the markup with shortcuts (e.g. ctrl+b), but not when you do it with the menu. By the way, the menu often obscures the content, it is quite irritating at times. Have you considered changing the algorithm for moving it around?
- Undo doesn't work for style changes
- Selecting text and changing to heading still changes the entire paragraph to heading