If you mandate and enforce it, you'll form/expose the hierarchy, right?
Well, depends on who "you" is and how you "enforce" it. Do you, the person given the systemic authority to do so, throw people in jail/gulags/whatever if they refuse to mask? Then yeah, that's hierarchical. Do you, a community member, organize with other community members to exclude the non-masker from social events and community spaces until they decide to mask? OR do you, a doctor designated via the community as an expert and thus given narrow, organic, retractable social authority to do so, say "you need to wear a mask"? Then no.