2. Syntactic sugar isn't just hand-waving; it has a reasonably-concrete definition. And it's generally considered acceptable if it delivers enough convenience (The concept of enough, you will find, is highly subjective.)
3. No one in this exchange has busted on the utility of SASS, so I don't understand why you'd deny anyone a SASS-like tool in a cage match nerd bake-off. For that matter, no one has busted on the practical utility of HAML in this exchange, just on the absence of new concepts i.e. powers of abstraction.
2. Reference me the official definition. Another point that didn't add anything to the discussion.
3. SASS been heavily hatred on in the past, Google it. Practical utility: Inofficially 80% of Rails/Sinatra developers use HAML - why? Because it makes people productive.