It’s been years since Kaeya has actually spoken to his father or anyone whose fully part of his home land
However over 500 years there must have been changes to the language so the khaenriah kaeya is used to is going to be different form what was spoken in king irmin times
So when he finally does meet another kheanrihan someone who speaks his homes language, Kaeya is most likely going to be kinda rusty to speaking and understanding it (yes this is massive angst potential but I want to think about the potentially funny situations this could bring)
Kaeya is going to STRUGGLE to understand Dainslief because This is the difference of modern English to Shakespearean English
Dainslief is saying “where arth though horses. If thou is this caverlay caption you speak of where is your stead?”
And kaeyas like “what.. what the fuck are you even saying”
Dainslief been only focused on revenge for years do you think this man would sit down to learn mondstadtian or even keep up with modern common? NO.
Kaeya most likely speaks like his grandfather invented chairs. Aka RICH person speak because that was what his father spoke like. So they can’t probabaly understand him either.
Don’t think albedo can help because it’s been years since he’s hear from Rhiendottir so he most likely too is not going to be used to speaking this. Not to mention he’s porbabaly used to only using super scientific terms, he probably speaks like hes in a science paper
So he’s going to be saying some “Kaeya would you like some hydrogen dioxide”
So Kaeya is completely out of depth here trying to talk to this medieval knight and this walking thesaurus
And diluc and jean just wondering what in the world are these people saying to make kaeya so upset and whether they should step in.
Seeing that Jean seems to know about khaenriahs existence based on that one voice line and diluc being straight up told about it they know that these people are most likely speaking that language. However they aren’t native speakers and anyone who could have easily taught them is dead
So now you have this friendship question where diluc and jean are digging through the archives to try to find SOME writings to help Kaeya Grasp his home tongue agaian. All while Kaeya kinda freaks out trying to find where he should stray (this Latin learner projection)