What’s the difference between “concerning” and “regarding”?

Solution 1:

This piece from the grammarist discusses about the usage of "concerning" and its possible overtones as "a cause of concern", but apart from that I think that it is interchangeable with "regarding":

• One complaint against concerning does stand up: The word is also a preposition meaning in reference to or regarding, and the adjectival concerning can cause confusion when readers or listeners initially interpret it as the preposition.

• For instance, if you hear someone say, “His email was concerning,” you might at first expect something to come after concerning. This complaint isn’t a rock-solid case, though, as many words in English have multiple functions, but it’s a good reason for those inclined against the word to continue avoiding it.

Actually checking with Ngram, (a question concerning vs a question regarding) it appears that "concerning" used as a preposition meaning "regarding" is quite common.