Regardless of the actual internal experience, it would be interesting that most people are quite certain they can "visualize" things, and a significant number of people are quite certain they cannot. This, in my opinion, would be worth discussing even if it was entirely down to the unreliability of people's self-descriptions.

However, the article mentions evidence that there is an actual physical difference here: fMRIs, and contraction of the pupil when imagining a bright light. Clearly something is happening.