Compared to the other Super-Family's, they are more brooding. Just look at past stories about them: Dick, shot in the head, Babs paralyzed, Steph brutally killed, and Tim was fairly miserable in the 90s apparently. Yeah, they mostly all got better (rebooted/retcon etc), but they are still a sulky bunch by contrast. And Kate was kinda 'emo' in her first solo, to the point where her family practically has an intervention and tells her not to try to do everything by herself.
The context of how and why she smiles has meaning. I can tell you from reading the comics, and re-reading them, that Kate does not come across to me as a genuinely cheerful character in any way. I like her for much the same reason I like Batman, but I do find her more interesting than Bruce.
I will admit, that Teaser with the Crow's guy was definitely contempt, but the Tattoo one was just strange to me - as I've never interpreted the comics version of the character as that ego driven. This live-action version is seemingly going to be quite different, I'm still adjusting.
*****
I've linked an article for you to read here, if you are so inclined:
http://www.bbc.com/future/story/2017...e-not-the-same
Also a key quote from the article for you:
And this article lists the sarcastic smile, that wasn't listed in the other article:Of 19 different types of smile, only six occur when we’re having a good time. The rest happen when we’re in pain, embarrassed, uncomfortable, horrified or even miserable. A smile may mean contempt, anger or incredulity, that we’re lying or that we’ve lost.
https://www.psychologytoday.com/au/b...what-they-mean