What’s wrong with low traffic categories, as long as they do have some?
Suppose that in the future a not-yet-existing subcategory acquires traffic withing an existing big category. How do we expect to ever make the split reasonable, if discouragement is our criterion? Cause the old big category will still have more traffic than any new one (as is the case with Usage anyway), so that discouragement will always stay in place. Or who will bother discovering and moving the past relevant threads from the chaotic big category to the new subcategory? Therefore we’ll get stuck to the few categories decided early. Is that desirable? Do you have a different positive scenario in mind? Or does current consensus fail the whole concept of categories?
If the subject of a category is worthy to subscribe to, then low traffic is a plus, not a minus!
The only encouragement to use a category is for it to exist. If users end up not categorizing their posts and moderators end up moving many threads all the time, why not give moderators more categories to work with, along with giving users more specialized subscription options?