adjective

Hi,
As I was looking for some help on where and when I should place commas between a series of adjectives, one thing that seemded to come up over and over again is that I should think in categories like opinion, size, shape, material, and others. The words belonging to "size" and "material" and some others seem to be easy and clear to locate

But in reality, it is hard for me to find out whether a word belongs to any of the group categories, especially one that belongs to the category of "opinion". It seems to encompass many things.

I believe I have used this before to ask a question:

long, thick, protective gloves

The use of commas seems to indicate a word in this series of words does not describe each other and if labeled in categories, they should belong to the same group cateory (If I could call it that). Do you think "thick" and "protective" belong to the "opinion" category -- I think not -- then, where do they belong (if they belong to a category at all)?

Another example:

a tedious, humorous game

Where do you think "tedious" and "humorous" belong?