Dia has the ability to add tags like (laughs) and (coughs) to cue non-verbal sounds. The TTS doesn't necessarily have to react to tags like this directly but there should be capabilities for saying something with a bubbly mid-chuckle tone, for example. More simply, being able to laugh when the user makes a joke is, in my opinion, an essential for immersive "empathic" voices. (I know Richard Marmorstein made a similar post but didn't include any details so I wrote this one)