I've reconsidered the system I'm using to evaluate writing instruments.
It occurred to me that the subcategory system was improperly emphasizing certain things and resulted in less-than-accurate results.
I have kept the same categories (roughly) and adjusted the scoring system. There are 10 categories which will be scored between zero and two; zero being a failure in all respects, one being "well-executed," and two being exceptional execution.
The updated system can be found here: writing instrument review methodology.