Interesting article. I've never heard of Slingfin before. Most of his point align with what I've heard from other knowledgeable people. Two things caught my eye:
1.
Because silicone keeps your nylon from soaking up water, fabric stretch due to moisture is greatly reduced and your fly (or tarp) will stay much more taught when wet.
I've heard the opposite i.e. the silnylon tents will sag more in rain. I live in California and therefore don't do too much camping in the rain, but I haven't noticed much difference between my two tents (one silnylon and one PU) in rain performance though they are quite dissimilar tents and difficult to compare.
2.
... silicone coatings can’t be combined with fire retardants to meet CPAI-84 standard....California restricts sales of tents made with sil/sil fabrics...
This really surprises me as my sil tent is a Tarptent that is made in California and they shipped it to me in California. I wonder if Henry Shires is skirting the law or has an alternative interpretation of CPAI-84 that has not caught on industry wide.