Main namespace should not be listed in $wgExtraSignatureNamespaces on Commons.
This configuration causes a signature button to be present on the toolbar: e.g. https://commons.wikimedia.org/w/index.php?title=Angraecum_filicornu&action=edit
…and, on pages where signatures are already present, causes [reply] links to appear next to them: e.g. https://commons.wikimedia.org/wiki/Coxeter-Dynkin_diagrams
It's accidentally configured this way, because Commons is considered a 'special' wiki, and they are configured this way.
'wgExtraSignatureNamespaces' => [ ... '+special' => [ NS_MAIN ],
But this kind of configuration is intended for wikis like Meta and WIkimania wiki, which are all about discussion and coordination between people.
There are currently only about 30 pages in the main namespace that contain a signature, most of them from 10 years ago: https://commons.wikimedia.org/w/index.php?title=Special:Search&limit=500&offset=0&ns0=1&search=-date_of_promotion+insource%3A"%28UTC%29"+insource%3A%2F%5C%28UTC%5C%29%2F