There don't seem to be any subscribe links at :en:Wikipedia:Categories for discussion/Log/2021 October 23, even though there are reply links. Will subscribe links be added on these sorts of pages? As you can see this page uses level 4 headings for each topic that should have a subscribe link, which might also be a problem.
Topic on Talk:Talk pages project/Notifications/Flow
I see subscribe links on en:Wikipedia:Village pump (miscellaneous), so the non-level 2 headings should be the cause. Since it’s currently not defined on the page that “topics” correspond to level 4 headings instead of level 2 ones (since there’s no way to define it), the software isn’t aware of this. Maybe there should be a way to define if topics on a page are not level 2 headings, for example a new magic word.
@GKFX, thank you for making aware of this case.
As @Tacsipacsi accurately described, Topic Subscriptions do not currently support non-H2 section level headings.
Although, we do have a ticket to expand this support and I've added the example you shared here to the ticket in Phabricator where we are tracking this issue: phab:T267288.