I think it would be nice if it Krita’s undo history wasn’t as fragile as it is now.
Currently, if you realize something went wrong ‘in the past’ and want to go back to recover it using the undo history, nearly anything you do in the past will undo the history. For example, if you go back, and select something to copy it that selection will be pushed onto the undo history, deleting all redos.
I think a nice solution might be to timestamp undo steps (if this isn’t done already) and ask the user to confirm when they are about to erase more than X minutes of work. I think this would strike a fair balance between preventing mistakes and not getting in the way during normal work.
Of course, this feature could be disabled and the X minutes could be changed to some other value.