Solutions that aren't 100% human-created aren't interesting in my eyes. The first one could have been, once, in the site's early days. But the trend I observe now is that they're becoming the default trick, just like UCS2 was a few months ago. So boooooring. And all the more demoralizing when the top voted answer in a thread is my solution, compressed by someone else. How lame can we get.
Solutions that aren't 100% human-readable could be okay if they're reasonably well explained, assuming the work to make them unreadable was human-performed, and seems task-specific enough.
I wouldn't like to see an arbitrary ban on any external library, though. I still see the search for the right way of doing things as a fundamental aspect of code golf. That includes finding the right tool for the job, who could be a library. In my opinion, the core issue is that we're seeing too many problems for which the right way of solving them is through dumb compression.
Obviously, kolmogorov-complexity is the usual suspect here. Maybe we should start devising a specific set of (default) rules for problems under that tag. I'd dream of simply punishing the problem submitter with downvotes when the winning entry is a compressed one, but that's far from populist enough to work. Our eternal September has started, and I'm not sure how to handle that gracefully.