Very interesting. The descriptions of CYA, Tri-Chlor and Di-Chlor are great, as is the explanation of why not to use it in an indoor pool.

But when they get to maximum and excess amounts there are problems.
Both points 4 and 8 are simply not accurate, and point 7 is misleading.
If you maintain a CYA of 30-50, you should NOT maintain a FC of 2ppm, but at least 3ppm. As CYA goes higner, you need higher minimum FC levels.

There's nothing unsafe about CYA in the 80-100ppm range. You simply need more chlorine. While it's true that CYA has diminishing returns as it rises, you can ALWAYS raise the level of chlorine enough to compensate.

Hidden in this article is the TEKTAT ("Things everybody knows That are true" but aren't) that chlorine should never be above 3ppm, which is nonsense.