The website looks like fairly typical junk science. In general, deuterium is chemically identical to normal hydrogen, so you're going to have to provide strong evidence to back up the claims that you're making.
I agree the website is junk, but the kinetic isotope effect is well-known in chemistry, so this statement is false.
If you are claiming they are identical chemically, I think it's you who should come up with Strong Evidence.
The common sense dictates that if a particule is twice as heavy, it COULD have different properties, which can be empirically tested, in fact WAS tested. (see links above)
There are differences in the chemical behaviour of deuterium, but those are only minimal.
Deuterium depleted water is produced by distilling water multiple times, which is extremely energy heavy operation. That's why a bottle of 1.5L 105ppm DDwater costs around $4. It is still extremely cheap if you compare to the cost of other oncology treatments.
There are minimal differences in the chemical behaviour. The very first scientific paper in the publication list shows the effects of that minimal difference. https://journals.sagepub.com/doi/pdf/10.1177/107327482199965... The results of deuterium depletion is what you see on Page 6: Decreased proliferation of cancer cells. In vitro studies were followed by animal experiments, which I mentioned above.
The human experiments were conducted on 22 persons. 2 of DDW consumers died, 9 in the placebo group died. This, as I see, doesn't rule out the possibility of an extremely efficient drug for cancer.
These are all backed by strong evidence, see here: https://hyd.hu/en/publications/
Please find the strong evidence here: https://hyd.hu/en/publications/