I would take the hard stand that any repetitive keystroke combinations inherently implies inefficiency - ie, an ideal editor should provide enough shortcuts to give your keystroke stream a fairly high entropy content. Maybe we're not there yet but I don't want to develop habits which would stand in the way of such an ideal.
But that's what the muscle memory is for. If you only ever used the arrow keys to move around and backspace to delete one character at a time, you won't need any special tool for memorizing which key to use!
The whole reason this tool exists is because the best text editors (Emacs ;)) do have a ton of different commands. So now you have to learn that when you wand to delete a word in front you use M-d.
The "muscle memory" is just associating each of the many discrete keystrokes with an action. So instead of thinking "hmm, I need to delete this word, I'll press M-d" your hands just go to M-d as soon as you realize the word needs to be deleted.
This is exactly the sort of memory you need to deal with a high-entropy command stream quickly. The ideal would be to use a ton of different commands without thinking about them at all.
Now, I don't think this site is ideal for this sort of learning, but it's a step in the right direction.
I don't want to need muscle memory for editing!
I would take the hard stand that any repetitive keystroke combinations inherently implies inefficiency - ie, an ideal editor should provide enough shortcuts to give your keystroke stream a fairly high entropy content. Maybe we're not there yet but I don't want to develop habits which would stand in the way of such an ideal.