A while ago I watched an episode of QI where Stephen Fry told everyone that knights would sometimes display some of their sins or characteristics on their shields.
For example, knights who tended to overindulge in wine would have a shield with a square of a specific color, or something of the like. I’m afraid I can’t remember any more details.
Now I really like this idea but I can’t find any reference to this custom on the internet. So, did medieval knights in Europe ever have the custom of displaying rather damning information about themselves on their shields or banners?
EDIT: I manged to track down the right episode of what I'm talking about, obviously I remembered the square thing all wrong!
From the QI website (theres also a video clip at the bottom) what OP is referring to:
The panel are shown a picture of a knight in full armour with his shield displaying his coat of arms and are asked what makes them think that the knight is a total bastard. The answer is the pattern on the shield. It includes a thick diagonal line from the top right corner to the bottom left edge, which goes across the leopards the shield displays. This is known as the "bend sinister" and indicates that he is of illegitimate birth. The shield also has a red background meaning that the knight shown is royal, meaning he is a royal bastard, also known as a Fitzroy. Charles II had five Fitzroys from his mistress Barbara Palmer. Other additions to a coat of arms to show dishonour, known as "abatements" or "stains" (hence "a stain on your character"), include the "point champaine tenne", a row of three spikes at the bottom to indicate killing a prisoner who has demanded quarter; the "delf tenne", a square in the centre of the shield to indicate cowardice, usually in the form of issuing a challenge and then bottling out; the "gusset sanguine sinister", a trapezium-shape section on the right-hand size of the shield which indicates drunkenness; and the "gusset sanguine sinister", where the trapezium is on the left-hand side and indicates adultery. It is possible to have more than one of these stains on your shield, so to have both gusset sanguine on your shield indicated both drunkenness and adultery in the same knight.
Follow-up question - if this is true, why would you have signs of dishonor on your coat of arms at all? Wouldn't you be the one deciding what to put on a coat of arms, and if you were, why have anything indicating you weren't totally awesome?