Hi!
Yes, your attention to detail is incredible - I've indeed created alternate voiceset for Xan and it works everywhere but in Xan-Kelsey and Angelo-Xan banters, maybe some other crossmod ones. Sorry! But if you would like Xan to be silent in these banters, you can still do it: open your override directory very carefully, sort by name and find .wav files AND WAV FILES ONLY starting with o#xan90 AND NO OTHER FILES, and delete them - again, very carefully. I would not recommend it to an unexperienced user, because you can incidentally delete Xan's main voice files and/or his other files. But if you've done something like this before (sorry if I sound pedantic, but I must address not just you here, but everyone else who might be reading this and trying this thing later), go ahead.