Thanks for the tip @riking. Glancing at that repo, it looks like it provides a “Use template as reply” button to expand week & previous week start & end templates. I don’t think that applies to this feature request.
The feature request is to allow some (hidden) text in a topic post that will automatically populate composer with a default value when people are replying within that specific topic. When requesting ideas, conference session topics, etc., it’s helpful to promote some consistency in the way people respond by using an ad-hoc template.