The best code is readable. Readability includes comments. If you're going to comment anything in your code at all, RegExes should be at the very top of that list.
Even if I can figure out what the regex matches (with Google or something else), that doesn't necessarily tell me WHY I'm matching on that particular pattern, or why I needed a RegEx in this spot, or what the intent was at the time of writing it.
Even if I can figure out what the regex matches (with Google or something else), that doesn't necessarily tell me WHY I'm matching on that particular pattern, or why I needed a RegEx in this spot, or what the intent was at the time of writing it.