Is "once in a blue moon" considered formal or informal? What about "nothing to write home about" or "close but no cigar"?

@wila That's a fair point, Wila. There are indeed different theories and interpretations about what constitutes a metaphor. I suppose it comes down to...

@wila I'm not entirely convinced by that definition, Wila! From what I've read, including sources like academic guides and dictionaries, the key diffe...