Affects Clothing?

Just making sure, since there isn't "Cloth Armor Mastery" and Cloth and Light are closely the same.

I think, don't quote me on this, I know about as much as you do, that only armors that can currently only equip 1 accessory, or usually start with a base 4/1 def/prot value count as armor, I think players with clothing as still left out.

Well prior to this update, endgame, it would be better to have a fully reforged and enchant clothing plus two accessories, rather than wear armor. These skills were made to counter that, so making a cloth mastery wouldn't really make much sense. Especially since, and this is my theorem, they're trying to define the line between Clothing and Armor. As both are put in gachapons but they try to make the clothing be the aesthetically attractive one and armor being the useful one so you not only buy more gachapons but also fashion slots.

You lost me at "better to have fully reforged and enchant clothing plus two accessories".

He is referring to having three items with good reforges, (clothes and two accessories) as opposed to two with light armor or one with heavy, since each item can have a reforge on it.

Can't Light and Heavy later get to wear more accessories?

Well I said prior to this update. This skill lets you wear more accessories and boosts the effects of light and heavy armor, which as I said is what I think they were trying to do to make people actually want armor too instead of just clothing.