I am kinda torn on my thoughts about this as a category.
Obviously, information about materials is useful. So that is the point for encouraging more such information.
My opinion against it would be: What would people talk about in each thread?
I assume each thread would be for a specific material. So you could say the material is or is not safe for using in a laser. Then if it is safe, discuss where to get it. Maybe give a few ideas for projects you can make which showcase the material? You could post the settings that work nicely for cut and engrave. A few images to show results.
So I suppose some discussion could happen. But it seems more fitted to a wiki style list of properties than a forum style (discussion based) framework.
There is a document which includes many links to information on materials