If you don't use the filled-in style, alas, the symbol looks like a fancy capital P, and thus you lose the typographic-related (pilcrow/paragraph) charm of the logo.
Agreed. On the other hand, the filled-in ones might not be seen as P-like at all. Though in the ones that jgm picked, that effect is not so strong through the serif.
The Vollkorn one does have a timeless classic look to it though. Does the license allow us to modify the Vollkorn (or Belgrano) symbols by bucket-filling-in the empty spot? The Vollkorn filled-in looks excellent to me.
I believe it does. Can you share your filled-in version?
C