Do Jane Austen's characters in Persuasion create a consistent idea of folly in the novel or are there some instances that don't fit with others?

Those characters whom Austen designs to be living by folly are
certainly consistent at it! Yet there are other characters who combine elements of folly with
sense who, from a casual reading, may appear to present an inconsistent picture of folly--because
they are inconsistent, but only by Austen's design and intent. First of all, the
definition of
folly in the sense used means foolishness,
stupidity, rashness as a state of personal being (an individual characteristic) or in regards to
an action, idea, belief etc. (derived from the Collins and Random
House Dictionaries on href="http://dictionary.reference.com/browse/folly">Dictionary.com).

Sir
Walter and Elizabeth are the two main characters who embody folly. An example of
Sir Walter's folly, that he consistently upholds throughout, is his inability to be realistic
about living expenses because he connects appearances of gracious living with his identity as a
baronet (which is the lowest class of hereditary titled commoner and ranked just above
nonhereditary knighthood):

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What! every comfort of life knocked off! Journeys,
London, servants, horses, table--contractions and restrictions ... No, he would sooner quit
Kellynch Hall at once,

Other examples
are the extraordinary power and importance Sir Walter attaches to the use of Gowland face lotion
(recommended to Anne and Mrs. Clay: “should recommend Gowland, the constant use of Gowland”) and
his silly, unseeing. all-encompassing vanity.

Elizabeth's primary
claim to showing unrelenting folly is her insistence that she must marry only a man who has a
baronet that is "worthy" of her own station in life. As a result of this folly (i.e., stupid idea
or belief), she has been the marriage-eligible belle of the social set balls for thirteen years
while her rejected suitors have gone on to marry ladies displaying far less
folly:

Thirteen
winters' revolving frosts ... thirteen springs shewn their blossoms, ... she had the
consciousness of being
nine-and-twenty.

The
Dowager Viscountess Dalrymple and her daughter, the
Honorable Miss Carteret, appear only briefly but give another very
good and consistent picture of folly (“Anne was ashamed. ... [They had] no superiority of manner,
accomplishment, or understanding”), which leads to consideration of the primary character who
inconsistently demonstrates folly, cousin William Elliot. At times,
William can show sense and reasoning power but his major decisions in life are based either on
maliciousness (which we aren't concerned about here) or on folly. The prime example of this is
his elopement with Mrs. Clay--the scheming, conniving, Mrs. Clay who
is herself a good example of inconsistent folly: “[whether] Sir Walter ... may not be wheedled
and caressed at last into making her the wife of Sir William.”