A "non-sporting" technique is one that is intended to, and has the capability of, causing permanent injury or worse.

Thats likely true, though do we train only the things that are taught in the Gym/Dojo?

I remember the first UFC's when the only things against the rules were biting and eye gouging. Ah, the good ol' days.

Many sparring techniques (especially in MMA) would fit that description.

honestly, any technique can cause good harm out there. Of course exercise some caution when engaging in something like sparring. And even more caution if you're going for like an eye gouge or a punch to the throat.

Ways to look at martial arts training:

For sport
For fitness
For fun
For combatives
For self defense (different than combatives)
For culture study

Why go at it just one way? If you embrace all six of these views on MA training, you'll never run out of reasons to keep learning and sweating. I think that's the pinnacle of what MMA should mean. Like it's already been said, the methodology is different than the prescribed 'system'.