Yes, I was very confused by the whole Nimitta debate before... I think I've actually read this article a few times. I've never had any strong visual effects when meditating - actually quite the opposite. The dark field that's covered with little moving spots and that tunnel of squares when I normally close my eyes tends to smooth out completely while doing concentration meditation. It's part of a general "smoothing" that happens to all the senses for me. I tend to use body awareness as an object, though, so maybe this is a "body awareness nimitta" haha...
The visuddhimagga, from what I've read of it, has a stong focus on kasina practice, so it probably was common for the monks using it to see a bright light of some kind. Eventually I just ignored the commentaries and went with the sutta definitions. It's pretty obvious when the body disappears that you're going into a "formless realm" - what else would it be?
I think there's an equally passionate (angry?) debate about how thoughts relate to the jhanas as well. Best thing, in my mind, is to look at concentration meditation like a slope rather than a staircase. You can ascend 8 jhana type experiences that match the descriptions perfectly, and then things flip over and 8 more stages unfold. Suddenly you think, wow, I must never have been doing jhana before! But then, HEY, another 8 levels appear. At that point you just give up and let it do its thing - that's when the really weird stuff starts to happen, haha.
