Where is Unfair Advantage in Wear?

At last weekend's Chesapeake Open tournament, the heat index reportedly reached over 100-degrees. Trees, umbrellas, shade tents, and towels were a respite for players on the sidelines. Players were seen with hats and bandanas - on their head and around their neck - when chasing plastic during the game.

According to USA Ultimate Rules (11th edition): "Players may wear any soft clothing that does not endanger the safety of other players or provide unfair advantage."

Back in July 2016, Matt Rehder (Sockeye) was seen wearing what is was actually part of his uniform; presumably the shirt's sleeve. The shirt-sleeve-turned-neck-wrap seems to fit within the definition as "soft clothing" and would not be considered as "unfair advantage."

screengrab via USAU 2016 US Open Men's Final

A handful of ultimate players were seen wearing more cooling performance products at Chesapeake Open to help battle the heat wave in the D.C.-area.

Could there be an unfair advantage by wearing more engineered products (e.g. Freezer Zero neck gaiter/bandana) which claims to: "which reacts with sweat to lower the temperature of the material" or other similar "ice bandana" products?

This question of active-wear that could potentially give an unfair advantage was originally raised back in 2012. This goes beyond the wicking ability of ultimate jerseys and shorts. Accessories are being designed based on activity and with a direct purpose of helping the wearer regulate temperature. Use on the sidelines is totally acceptable, but wearing for example a cooling neck scarf while playing could be seen as advantageous.

1. Where do you draw the line in the temperature-regulating  performance wear? Undergarments and/or outerwear?

2. Who enforces whether an unfair advantage is being gained from what a player is wearing? Observers and/or players?