I don't see "pietnas" anywhere; do you mean the "important_numbers" example from maratc?

If so, I think a trailing comma is the correct fix, as described here: https://news.ycombinator.com/item?id=45168308

In this case I think the trailing comma is an improvement, so the formatter is steering you towards a better overall solution. However, even if you dislike the trailing comma, it's more important for the formatting to be consistent and robust, so I still think it's better to work within the limitations of the formatter.

I honestly have no idea where I read pietnas. The comment you identified was the one I was referring to.

I care about consistency, but not foolishly so. I suppose an important question is: under what circumstances is consistency undesirable?

I believe that consistency is not an end goal, but a means to achieve clear communication. When being consistent results in less clarity, it should be abandoned in favor of more effective communication.