From you description, they were clear and consistent with their 8:30 policy. So asking the waitress multiple times didn't make it more probably to change the rule.
"佢嗰朋友對住D Sushi咳"... so that 朋友 is a customer? siting at the sushi bar? It's hard to tell customer not to cough. But they should look into adding cover between the sushi bar to the sushi table.
so I guess that gives all chinese restaurants and their staff a right to serve "attitude for free & crap face complimentary" oh...also...don't forget to ask "us" for our "daily Talk-back in bad breath" deal...
resent chinese restaurant and shame of being a chinese in this aspect.