Thanks for adding this context, Sam. I had found some but not all of these topics and thus only had an imperfect understanding of the misadventures of undoing in Discourse.
I don’t like being accused of going round in circles or opening cans of worms, but I guess in this case it’s true 
I’ll stand by my earlier point: from a joe user’s perspective not being able to undo syntax changes looks like broken/missing functionality.
I’m having trouble as it is getting my users to buy into using Markdown. Having a Markdown editor that is so limited increases the difficulty. In general, the editor is quite weird. Would it help to begin cataloging the issues/limitations, or is there an existing list somewhere?
(I’m sorry I don’t have anything more useful to offer than some gentle bug reporting.)