From my point of view, this distinction is bad in itself.
Builders want to install a module to solve a problem
But if there isn't any, why should we limit answer to "cannot do", when thing is perfectly doable with some coding?
Developers can just build one
But really, why should they? It would be better use of their time to join efforts with developers of module that already is doing the same thing, thus creating one, better supported module. and even if they want to code it themselves anyway, existing contrib opensource module is perfect resource, comprehensive example how to code such thing.
For the intended audience issue:
This site is not a forum. It's meant as knowledge base, and intended audience are future readers. Most of them probably unregistered first-timers who just found it using Google or something, because they had Drupal related question. You can never know if they are coders or not.
Only if question is asked in a way that makes it clear that only one side is an option you can reasonably expect people googling for another one not to find it. Google and other search engines will not obey tags here, so for most of the audience (or at least large portion of it) tags are useless; any similar mechanism will be.
Only things that will be useful for future readers are:
- Questions with as many different correct answers as feasible
- Questions that are so clearly about code that "system builder" will not find them by accident, and vice versa