> All that really matters is consistency

And this is my problem. My last example, the 2 styles are inconsistent. So when the guideline is "all that matters in consistency" then I take that at face value. You though apparently pull back and believe something more messy. Effectively "All that really matters is a consistently applied style even if that style itself is full of inconsistency"

The same applies to the trailing commas. With them, every line is consistent. Without, the last line is inconsistent with the other lines. So are we applying this rule "All that really matters is consistency" or only applying it sometimes? I would argue whatever heuristic made you say "All that really matters is consistency" should apply to both cases. Consistently apply a style guide and, the style guide itself should be consistent.

> Without, the last line is inconsistent with the other lines.

The last line without a comma imparts the information that this line is expected to be the last line in the list which is something you don't get from it with that trailing comma. It's a small thing, but I don't like putting in that last comma because I'm effectively misrepresenting things for "syntactic sugar".