Can testicular torsion cause only mild pain?

Torsion: It could if its intermittent but is hard to say not knowing more information.

Not usually.: I suppose that mild intermittent twisting of the blood supply could cause mild and intermittent discomfort. But, i really don't think that is likely. Torsion is usually an acute onset of horrible testicular pain often associated with nausea/vomiting and abdominal discomfort.

Yes, if ...: If being mild and intermittent twisting, yes, its related pain can be mild. Again, remember: every life event always displays itself as a pattern of full spectrum, and we only assess the event at certain point or moment on that full spectrum, at which we have to make a good decision and take a good action so to expect a good outcome. That is our professional life.