That’s my best idea of a description for a showcase subcategory. I’m honestly terrible at coming up with names, but something like #showcase-discussion might be fitting - especially because it would make it clear that the subcategory is for discussion, not advertisement.
To combat the fact that people might be inclined to advertise there, I would probably suggest naming it something like I mentioned above - a name that promotes discussion. You might want to revise my suggested ‘About’ section for that subcategory, too, to really emphasize the fact that discussion is the subcategory’s purpose.
I would probably suggest that non-regulars should use Post Approval to post in a showcase category, to reduce advertising, but anybody of any member+ rank can reply.
To Be Clear
My suggestion is that the specific support categories be used for in-depth technical support, as you put it, cool-creations be used for general feedback on development, and a showcase category only for displaying and discussing completed projects.