Can someone explain 衣锦尚炯 character by character?
You probably mean 衣錦尚絅 here.
衣：to wear
锦：brocade (clothes)
尚：to add
絅：unlined outer garment, usually made from linen
Literally the phrase means &quot;To wear brocade inside, and add linen overall robe outside&quot;
The phrase was originally from 诗经 as in “碩人其頎，衣錦褧衣。” where 褧 is a interchangeable character to 絅. And 中庸 as in 詩曰：『衣錦尚絅，惡其文之著也。』
The phrase is a metaphor that real noble people would hide their virtues under humbleness.