You have to be wearing the trunks for them to talk.
I do. My Scarlett wore them for more than 5 hours now and not a single word from the trunks. Playing on the latest version all the time of course. Hm...
The trunks comment when you level up, break something (door, chest, barrel etc) or steal something.
It will also read out all gravestones in voice, so try a graveyard.
I haven't noticed any other commentary.