It looks awful but lets you comment out the last of a comma-separated group. (I still use trailing commas)

I hate visually parsing leading commas, but it’s clear they make commenting out lines easier. If you comment out the last line, you don’t have to comment out also the comma on the penultimate line.

I don’t know SQL but I’m a leading commas diehard (where it makes sense in C++ and Haskell).