REPRODUCE:
open an article in enwiki or hewiki, with at least one section edit, for mobile view.
note that the pencil icon to the right of the section name (or left, on RTL wikis) is not visible.
the button is still there - if you are a good marksman and know where to push, you can still edit the section, but in practice, it means mobile edit is disabled.

i find it strange that this is not a dupe (maybe it is) - i could not find another report.

fwiw, i added to mediawiki:minerva.js on hewiki the following line, and the pencils are visible again.

$(function() {$('h2.section-heading a').addClass('mw-ui-icon-wikimedia-edit-base20'); } );

peace.