https://nl.wikipedia.org/?diff=57433885
There is a numbered list beginning with #<li value="5">, which (I think) is supported in a hacky way in Parsoid. In the edit, items of a nested definition list were pulled out of that numbered list (the leading # disappeared).
This is probably some old edge case bug (nothing to do with selser or discussion tools)
[subbu@earth:~/work/wmf/parsoid] cat /tmp/lwt
#<li value="5"> a
## b
[subbu@earth:~/work/wmf/parsoid] php bin/parse.php --wt2wt < /tmp/lwt
#<li value="5"> a
#b
[subbu@earth:~/work/wmf/parsoid] cat /tmp/html
<ol><li data-parsoid='{"stx":"html","liHackSrc":"#","autoInsertedEnd":true}'>a<ol><li>b</li></ol></li></ol>
<ol><li>a<ol><li>b</li></ol></li></ol>
[subbu@earth:~/work/wmf/parsoid] php bin/parse.php --html2wt < /tmp/html
#<li>a
# b
# a
## bI am inclined to remove the parent task but not sure if it impacts any of your tracking on discussion tools reported issues.
Change 639280 had a related patch set uploaded (by Subramanya Sastry; owner: Subramanya Sastry):
[mediawiki/services/parsoid@master] Fix old wt2wt bug for listed nested in li-hack lists
Change 639280 merged by jenkins-bot:
[mediawiki/services/parsoid@master] Fix old wt2wt bug for lists nested in li-hack lists
Change 641308 had a related patch set uploaded (by Subramanya Sastry; owner: Subramanya Sastry):
[mediawiki/vendor@master] Bump wikimedia/parsoid to 0.13.0-a17
Change 641308 merged by jenkins-bot:
[mediawiki/vendor@master] Bump wikimedia/parsoid to 0.13.0-a17
Very similar issue from 13 November: https://vi.wikipedia.org/?diff=64043608 (this is before the patch was deployed)