So... let's continue and branch off of the argyle hose thread. Based on that thread and a couple others with these discussions, many things may not fit the tighter definition of THCD. Thoughts on the following (some of which I may break, at least on occasion)....

Hair sporrans for anything other than formalwear - NOT THCD
Glengarry caps - NOT THCD
Bonnets (Balmoral and Tam)- Still THCD, but fading away
wearing clothing too smart for the occasion - NOT THCD
wearing a belt with waistcoat but no dirk - NOT THCD
Belt with dirk for daywear - NOT THCD
Bowties for other than formalwear - NOT THCD
Flat caps - NOT THCD
Wearing THCD for something other than a Highland type event or special occasion - NOT THCD

** Note, none of the above relate to pipe bands or military