Meta Keywords; To Comma or Not?

Want to get old school today? Search Engine Watch Forums has a new thread asking one of the oldest questions out there in SEO. The thread is named META Keyword Strategies and asks;

I was wondering if anyone had any thoughts on the strategy of not implementing commas between the keywords in the META tags:

i.e. {car accessories, auto parts, mufflers} vs. {car assecories auto parts mufflers}

Most say it doesn't make a difference but Danny Sullivan notes that the last time he spoke with Yahoo! about it, "they said to use commas."