When typing "myMemo." and pausing, i get the suggestions display and "CanUndo" is shown with a red padlock.
You are talking about typing into the source editor of the IDE?
Not sure, but from a quick look: the red-padlock indicates a read only property.
That is correct: "TMemo.CanUndo" is read only. If it returns true, then you can call "TMemo.Undo" and something will be undone.
If "TMemo.CanUndo" returns false, then "TMemo.Undo" will do nothing.
As for the rest, please report on the bugtracker.