[mulmen]

I hear this argument all the time but it makes no sense. Leading commas only help you comment out the last line. Any comma arrangement allows you to comment any intermediate line. It’s sacrificing readability and aesthetics for a tiny benefit on one row.

[arh68]

likelihood of commenting out last N lines >> .. first N lines

What happens is I want to comment out a join entirely, and all its columns. I rarely find myself commenting out the first column. I'd prefer trailing commas on every element, where allowed, to be sure! but leading isn't so bad once I got used to it.

Plus to scan for a missing leading comma is a linear (literally!) search whereas [missing] trailing commas don't line up.