Hi Chinn_asama,
You are correct that 2 (or more) adjectives ARE USUALLY separated by a comma (or commas). However, the GMAT writers have shown some flexibility when it comes to "style" rules and the English language includes 100s of idiom phrases that "just are" (meaning that history has made them into established patterns). The good news is that most SCs are based on 2-4 grammar rules, and you can usually choose the correct answer without knowing all of the rules involved. If you're not sure about an issue, then look for another one that you DO know.
Your example....
" the decision was taken amid widespread public outrage"
could have been written this way....
" the decision was taken amid widespread, public outrage"
But both are correct.
"Punctuation" is not a category in SCs, although punctuation does play a role when dealing with certain grammar rules (modification, parallelism, comparisons). While it's a rare issue, you might see a semi-colon used in 1 SC on Test Day, but that's a separate style rule. SCs are built with 1 right and 4 wrong answers - there will never be 2 correct answers on Test Day. The above example would not occur.
GMAT assassins aren't born, they're made,
Rich
