I don’t follow. Marked definitely isn’t a programming tool. There’s nothing about Markdown that says nested lists should look like code. That’s just an accident of whatever editor you might be using, not of others.
…as long as you ignore the context that it’s a nested listed under a less-nested list.
Also, note that CommonMark is not identical to Markdown. It intends to be a standard definition of the language, but may differ from the original definition and implementation.