An alternative is to use a workflow. For example this action does something in
that line:
https://github.com/marketplace/actions/pull-request-ticket-check-action
I think including the a PR comment check in the PR checks is a great
idea if it is feasible: If a section is blank, the check fails.
That check would only mean that the contributor wrote something each
template. That does not mean that the comments are good, correct, or
usable.
Comments are ignored in the PR templates as well. We used to have a
long, useless PR template with lots of comments. It was always igored..
by everyone. So I do not think that adding any kind of comments will be
useful at all.
If that is feasible, could we do the same with commit comments?