Hoping someone familiar with the subject will find this.
In Thm 4.1 of this paper (p. 14), it says that the irreducible characters of a finite algebra group (like the unipotent uppertriangular matrix group) are exactly the characters $\phi_{\mathcal{O}}$, of which you can find the definition on p. 3. They are just the Kirillov functions, right (?), and I thought a big point (proven by Isaacs and Karagueuzian) was that the irreducible characters of the unipotent uppertriangular groups are not always Kirillov functions?
I was very confused by this, but can't find anything anywhere redacting this paper, so I must be misunderstanding things.