Not sure if you mean in the Discourse chat function. If you do, then I figured out how to do it before by modifying the chat template, but the chat template kept changing so much that I got tired of updating it for each change.
If that’s what you meant and want to know more how I did it, let me know and I’ll post more here.
Ideally, I’d also prefer it was an option in core. I love how WhatsApp and Signal and I think most chat apps show the message in the reply indicator.