It would be great if we could edit what each entity can say with chat bubbles. The villagers dialogue don't really make much sense for my pack and are immersion breaking.

This feature has been discontinued.

Turns out they're (were, in 1.12.2) in en_us.lang files, meaning it should be possible to overwrite them using a resource pack.

Create a resource pack with the file structure assets -> dsurround -> dsurround -> data -> chat and inside the chat folder, place a customized en_us.lang file containing whatever entries you want to overwrite. While I haven't tested this myself, in theory it should work.