… on mobile devices, because of the sticky header.
Can you can take this up upstream? They are usually quite responsive in their community forum - https://community.nodebb.org . I think your point about the mobile screen space being drastically reduced is quite valid. You can see same behavior in their forum as well on mobile.
Yeah, I threw some feature requests in their Github (like increasing the size of the upvote button on mobile so you can actually hit it) and I think they already committed code to fix it. So I'm sure they'd do the same for your suggestion, since it's a good user preference to have.