On Usury and Catholic thinking

So I posted about the tendency within Catholicism to emphasize obedience to the Church.  Obedience beyond what most traditions tend to emphasize.  That post was here.  But check out the discussion between two guests.  It takes on the issue of Usury, one I admit I don't grasp that well.  I know if it mostly from studies in Medieval History.  Haven't really thought about it otherwise, or at least not in its spiritual ramifications.  Anyway, the subject is beyond me, so read some back and forth between two individual inefficiently more schooled in the subject than I am.  For me, it's like Fay Wray watching Kong fight the T-Rex.  Just hold onto the tree and wonder.