Probably we can introduce a new level of verbosity, but I am thinking so this behave is reasonable. Everybody who use a VERBOSE level expect lot of balast and it show expected info (context of error)
Can be this design good enough for you?
I like the idea, but I think this should be a new verbosity level. With this patch you would have to go full VERBOSE just to debug PL/pgSQL code with NOTICEs and DEBUGs in it, and that output then becomes harder to parse with the useless C-code information.
word "DEBUG" is not good - it is used for Postgres debugging as log level