As I guessed you don't really want to have plaintext. Again, try turning off markdown extensions to make it more "lightweight" and tailor that as your "plaintext".

Regarding treating list marker as plaintext or not: we need to ask ourselves what do we mean when we say plaintext and markdown. In the "markdown wins the plaintext war" camp, markdown is plaintext. Just to look up wikipedia in <https://en.m.wikipedia.org/wiki/Plain_text>, non-binary formats are plaintext, like most of the pandoc formats including HTML. So pandoc's plain format definitely has a special meaning than these. And @jgm just defined it above. Lastly, when I say the list marker isn't plaintext, I'm thinking in terms of "stringify". Like if given a document, if I'm to remove every formatting features, what would I be left with? Or in other words, if I speak it out without any help from those markups, what would that be? In this sense, a list in *plain* text is like "Give me a pen, pencil, and ruler." By the way, I think in typography, when you write that in a list (with list markers), the rule to apply punctuation marks and connectives is exactly as if you write it out in a sentence. i.e. the list marker is just a visual element to better represent the information.