I’ve tried everything. All I can think of is that something went awry when my custom coder paged the comments, but disabling that function isn’t solving anything.
To reiterate:
All previous entries are fine, with working comments and visible comment fields.
On new entries, the comments field is not showing up. (And I don’t know if that means comments aren’t working on new entries, because without the comments field visible, there’s no way for me to add one.)