As a high school teacher I can confirm that I have never heard a teenage girl say "uncomfy." Honestly, I think most of the twee 'teen' speak is said by people in their 20s and 30s.

There's a Youtube essayist called Kyle Kallgren who described the current trend for nostalgia and hating everything that might challenge it such as the new She-Ra cartoon as "adults who are furious that they are no longer children," and I'm starting to wonder if that applies to a lot of tumblr culture such as the cutesy twee stuff as well.