The trailing comma rule is to avoid errors when devs copy/paste a line or dump a new line at the end. This matters particularly for arrays in languages with implicit string concatenation, where the missing comma won't trigger a compile error.
yes, and isn't it funny that
foo=[baz, bar,]
returns a nice list of two items, but if you edit this down and miss the comma,
foo=bar,
is not a scalar.
returning a tuple.
So the trailing comma thing is a thing.