Is the 10% service charge mandatory or voluntary in HK?

[Guy_in_HK]

Pay it and get your pound of flesh with a Google review.. that's what the kids do these days.

I think more kids in HK these days use openrice or even plenty of other review apps and/or whatevers these days.

Don't forget the majority of HK tourists often don't usually have direct access to Google stuff, so they use their same restricted stuff wherever they go if those copycats work well enough for them.