No - as the OP said, “…you have to put a comma after the year in a month/day/year date configuration…”
Personally I would avoid using a month/day/year date as a modifier because it is damned ugly.
So, as filling_pages suggested, you should recast the sentence. I would go for:
“A revenue shortfall of 23% resulted in Mr Jones being laid off on May 6, 2010.”
I know the OP also said “Don’t try to fix it so the construction is different- I need to know this globally”, but I think not using a date as a modifier is a pretty good rule to use globally if you want to write clearly. Fixing the construction is almost always the best method when you come up against dilemmas like this.
There is one instance where this is inapplicable: transcription. You can’t change what someone said, regardless of how clunky it is.
Personally, I try to avoid unnecessary punctuation. “The May 6, 2010, layoff” is not semantically or syntactically different from “The May 6, 2010 layoff” so I would go with the latter in the absence of a style guide, and possibly even “The May 6 2010 layoff” if I felt daring.
Put the comma in. Without it, it looks like “2010 layoff of Ms. Jones” is a clause, but it isn’t. if you start an extraneous clause, you have to terminate it so the reader knows where the sentence “comes back together”. #2 looks like two separate statements whereas #1 looks like just one. If you want to drop the comma, I say you have to drop both, i.e:
A revenue shortfall of 23% resulted in the May 6 2010 lay-off of Mr. Jones.
You can always write it military-style, and my personal preference: 06May10. It’s short, easy to read, and ordered chronologically. If you want to dress it up a little, go with “the 6 May 2010 layoff”.
Either way, 2010 is part of the date, not the layoff, so you can’t punctuate it to look like it’s separated from the date. You need two commas in there.
I disagree. As Chessic Sense has just said, that makes it appear that “May 6” and “2010 layoff” are two separate clauses. Use two or none, if you must.
I can’t think of any instance in which “The May 6” is viable as a fully-contained clause, nor a clause that starts with a year and a noun, that would lead to ambiguity. Perhaps if you had a ship named May 6 or something. It hardly appears confusing or a garden path construction to me; the comma is simply a part of the date construction, just as it would be part of a dollar amount. Adding a comma after the year introduces a hitch in the sentence that shouldn’t be there any more than in another, noun phrase.
I don’t think I’ve ever seen a style guide that would allow no. 2, but I suppose I could be wrong. If I ever did find one, I’d be immediately suspicious of using it!
I agree with your boss and with your boss’s reasoning. The year is essentially an appositive, which has to be set off with commas. We don’t think of it that way, but changing it means eliminating both commas, not one.
ETA, if I saw no. 2 in a document, I would assume that it was an error and that the document was poorly edited. I would not immediately think it was a stylistic choice. That may be more important that whether it can be justified as correct.
The rule is actually that you need a comma after the year ONLY when using format month, day, year. There is one very important exception, however. If the date is used as an adjective (e.g. the June 1, 2010 disclosure), you do not use the comma. Never use a comma to separate an adjective from the noun that it describes.