I really like that Mou is also a linguist of sorts. It's fun to see both of them try to figure out what's going on, starting from different cultural perspectives, and seeing Mou able to figure it out much faster due to that.
I wouldn't even know what rutile is in the first place if it wasn't for Land Of The Lustrous. People should search for how rutilated quartz looks in real life, it's awesome!