The link on the last [Edit source] button on the page at the moment is https://fr.wikipedia.org/w/index.php?title=Wikip%C3%A9dia:Le_Bistro/2_mars_2020&action=edit&section=T-14 It works in the 2010WTE (which disregards the section number?) but not in the 2017WTE. I don't know if the problem is really the the editor or the link.

This is related to transcluding the section from another page.

Looks like the new wikitext editor doesn't handle section numbers prefixed with 'T-' correctly. I think they are supposed to count section headers defined inside <includeonly> tags, like the header =Le Bistro/2 mars 2020= on that page, while normal section numbers don't. NWE just removes the 'T-' and pretends it's a normal section number.

I don't think that this scheme is documented anywhere, and I'm not sure if that's the only difference. I would need to read some code to figure out how exactly it's supposed to work, and how we should make use of that correctly.

Change 581081 had a related patch set uploaded (by Bartosz Dziewoński; owner: Bartosz Dziewoński):
[mediawiki/extensions/VisualEditor@master] Remove incorrect handling for 'T-' prefix in section numbers

https://gerrit.wikimedia.org/r/581081

Well, this was easier than I expected. Hopefully we won't discover that I missed something obvious.

Change 581081 merged by jenkins-bot:
[mediawiki/extensions/VisualEditor@master] Remove incorrect handling for 'T-' prefix in section numbers

https://gerrit.wikimedia.org/r/581081

QA note: this is not expected to work correctly on mobile, as the mobile skin generates those links wrong (T198011).

(I think I fixed T198011 too, so it should work on mobile as well.)