I love it how Aha! does great work with communication when the user has "emotionally loaded" moments, such as Shipping a product. There, for instance, when the user is shipping the product, Aha gives a message:
"Good work. Every feature in this release has been completed!"
Does the message need to be there? No. Does it provide extra value? No. But it still makes you feel better and makes Aha feel more conversational as a platform.
What I'd do in these places, I'd focus the user even more on the emotional moment by highlighting the message, and perhaps using some of Aha's characters already used int he web site to make the message even stronger.
Attached are a couple of very very rough sketches (with totally irrelevant gfx) of the idea.