The Brief: The upside-down face emoji expresses playfulness or sarcasm.

DEEP DIVE
This emoji can also be used to express a lackadaisical attitude, usually in response to something more serious. A word-based translation might be a playful “oops” or “oh well.” It can also connote a mix of happiness and sadness. The upside-down face emoji is closely related to the shrug emoji.
You can stop dying now. π pic.twitter.com/UIMXB8cFGs
— GameSpot (@GameSpot) February 20, 2019
How is life going? π pic.twitter.com/cE8UNMo2O4
— XANTHE met X en H (@XVerstreken) February 20, 2019