You can Ctrl+select multiple languages. Do you also have Undetermined+English+whatever else is relevant set?

In my experience the federation issues others are referring to don’t report missing comments because they aren’t technically there on anything but the home instance so I’m inclined to believe it’s something different.

Go to your settings and make sure your language preferences include “undetermined” as well as your preferred languages. Lemmy only shows comments that match your preferences.