There was a story here a while back about how the Twitter/Bootstrap developer was arguing with Douglas Crockford about whether or not he should have to insert semicolons. The cause of the argument was the fact that the minifier was changing the meaning of the code, IIRC, by preserving semicolon preference.
Right, but that was JSMin, which is more of a souped-up find and replace, whereas this comma-replacement strategy is what you'd expect from a much more sophisticated compiler which does static analysis and complex code transformations to squeeze out more than you can achieve by simply compacting white space and deleting comments. That level of modification would be crazy and fragile if you were modifying the original source code, so it's a fair bet that ASI is irrelevant by the time you're looking at the compiler output.
