I wouldn’t. I would expect a formatter to preserve comma-delimiting.
I think the best way to address the formatter topic is that a formatter should follow the rule suggested by @John_McCall that each list should either have commas or not have commas. They shouldn’t be mixed. With this rule in place, a formatter would preserve the choice of the author. If the author wrote a mixed-comma list I think the formatter should insert commas everywhere to be conservative. If the author does not want commas they can be manually removed.
As I have said before, I think comma elision is wonderful sugar when used judiciously. I don’t think it should be applied everywhere it is possible. Deciding when to use it requires both technical and aesthetic judgment. I expect the most common cases where it makes sense will be EDSLs and literals made up of raw data.