And the point was whether u/w light can be any more harmful (or annoying) than swimming surrounded by finely shred sh!t and toilet paper.
We can agree to disagree of course, but even if I have no u/w lights on my boat and I'm not thinking to fit any, when I'm in a secluded anchorage I still prefer to be surrounded by boats with u/w lights and black tanks than boats with neither.
But aside from agreeing to disagree on that, I'm afraid you're totally wrong on the following:
Suffice to say that one of the most critical issues with those tablets is that they must be perfectly water-soluble, because if even the smallest grain remains suspended in the water and it gets in your eye, you can wave good bye to it...!
There are other products meant to colour urine, in order to show who's doing what (used mainly in public swimming pools, obviously). But what makes your eyes sting is definitely chlorine, nothing else.
In fact, while at sea I swim with open eyes, I NEVER do that in any swimming pool. And I'd strongly suggest you to do the same (or at least use googles), if you regularly swim in pools.