O.K. Here goes… Whenever I’ve found a 14 gauge wire on a 20 amp breaker, I’ve always said it was a safety hazard for reasons we all know. Here’s the tricky part. I spoke with an electrician in the area that told me on older systems, it was fine (but not for new construction). Apparently, a 14 gauge wire can carry 20 amps safely but the “powers-that-be” say it can only carry 15 amps just as a built-in safety measure.
My gut feeling is still call it out as a safety hazard but technically, according to this electrician, it’s O.K.
In all honesty, the older code was generally more stringent on conductor ampacity. Like all has said, the electrician was dead wrong. I could not tell you how many misinformed or underinformed electricians I have dealt with over the years. Quick reference books are a major contributor to the problem.