Our word "sincere" comes from the Latin "sine cera" meaning " without wax.
There is some disagreement as to WHY sincere means without wax. My favorite is this one:
Apparently, unscrupulous marble statue salesmen would rub white wax into cracks in their statues making the cracks disappear. Later, in the heat of the atrium, the wax would melt exposing the cracks.
Reputable statuaries began advertising their statues as "Sine Cera" ... without wax.
So, sincere doesn't mean one has no faults, but that the faults are not disguised.
Where else but AA can you go to find a room FULL of people trying to dig the wax out of their cracks?