originally reported here: https://www.mediawiki.org/wiki/Topic:Vs45qklj0xx2tqox
DiscussionTools' reply widget doesn't open in the first section ("Hana Krampolová") on this page: https://cs.wikipedia.org/wiki/Wikipedie:Diskuse_o_smazání/seznam
Opening it in VE, something immediately looks wrong, as the text of the next section is directly editable, even though it should be part of a transclusion: https://cs.wikipedia.org/wiki/Wikipedie:Diskuse_o_smazání/seznam?veaction=edit
…and the section itself has the expected transclusion syntax for the next section as a part of its "content":
The Parsoid rendering for the page is here: https://cs.wikipedia.org/api/rest_v1/page/html/Wikipedie%3ADiskuse_o_smazání%2Fseznam/18926832?redirect=false&stash=true
The nodes belonging to the broken transclusion are marked with about="#mwt5", but the "initial" node (which would have the typeof="mw:Transclusion" attribute etc.) is missing.
The section node is actually correctly marked as a transclusion with about="#mwt8", but both VisualEditor and DiscussionTools remove the section nodes.
Here's a copy for reference:
I am guessing that this might be caused by the HTML comment at the beginning of https://cs.wikipedia.org/w/index.php?title=Wikipedie:Diskuse_o_smazání/Rajlichova_hypotéza&action=edit: