I'm not entirely certain this is a bug, but it seems counter-intuitive, so I'm going to post it here instead of suggestions. Currently, an armor vest below 50% gives the "wearing frayed apparel" debuff. It seems like only actual clothing should give this debuff, and equipment such as armor and weapons should not.
I think the problem here is semantics. Apparel can mean anything you put on. Like watches. It is also a verb "to get dressed". If you analyse that as well, to "get dressed" doesn't mean you put on a dress. Hell, "toilet" can actually mean to get dressed as well as it's meaning is just to clean/prepare/clothe yourself (which can include TONS of things).
Also, you are damn right I would be complaining about being the guy with a junk weapon and bullet proof vest.
You don't think you would complain about using a used/damage bullet-proof vest? They are one time use. Once you have been shot in them, they are no longer safe to use.
You're right, I'll change the text.