To this still empty thread: how about we just stop arguing and add these damn commas everywhere? How about having human- and devenv-oriented languages finally, after how many decades?
The first case that jumps to me: if you write "a,b,c," you can't know whether you forgot a parameter, you passed an empty string where there shouldn't be one, or you intentionally left a trailing comma. And SQL already is human-oriented - compare your typical SQL to a data operation in K [2]. It just so happens that some things are hard and off-by-one errors are famously near the top of the list [3].
Whenever a database complains that your SQL query contains a trailing comma it's a sign that you may not have paid enough attention to your arguments (or even worse, that you're building queries by hand instead of using prepared statements). From where I stand, not allowing trailing commas is a feature, not a bug, and I would therefore object against them.
[1] "be conservative in what you do, be liberal in what you accept from others" - https://en.wikipedia.org/wiki/Robustness_principle#Criticism
[2] https://news.ycombinator.com/item?id=42999650
[3] http://www.randomprogramming.com/2014/09/quote-of-the-week-h...
SQL is fundamentally unsafe "forgot the item"-wise. It doesn't allow dynamic column selection, there's no type safety, nothing. If you want guarantees, maybe make a proper language with guarantees rather than justifying random side-effects of a comma being a syntax error sometimes.