In Ch. 25 Catherine is impatiently awaiting a letter from Isabella:

But Isabella had promised and promised again; and when she promised a thing, she was so scrupulous in performing it! This made it so particularly strange!

I read this passage as meaning that Catherine is scrupulous in performing what she has promised and expects others to do so.

James also ascribes attributes to John Thorpe which are most likely his own:

Poor Thorpe is in town: I dread the sight of him; his honest heart would feel so much. I think James and his honest-but-wounded heart is worthy of a sequel!

James's sentiments are written before Thorpe's failure of a very recent endeavour to accomplish a reconciliation between Morland and Isabella, (Ch. 30). I wonder if James is ever undeceived about Thorpe's heart? Catherine in the end declares Isabella to be heartless (bravo!); I'd like to believe that James comes to understand what a dolt and bloviator John is, as John is now spurning a friendship [with Moreland] which could be no longer serviceable. (Ch. 30)