I think it's where you take the Max Str Req of any item and subtact it /w Str from items/charms/your base Str/etc. Then you get just the right amount of Str including items/charms and you will look naked.
As long as you don't have enough strength to show the gear without items/charms but do have enough with items/charms then that gear will not show up. You will still see your character weilding all of his gear, but the other players in the game will not. You can never actually see your own character str bugged. Well, unless you have another account... but yeah, not under any normal circumstances.