airlines are and always have been high profile companies that evoke a lot of emotion from a lot of people.
I'm not sure that there is any basis for a DOT investigation based on the amount of DL's disclosures... but perhaps as a supporting document to their ongoing concern about airline fee disclosures.
but since there has been no finger pointing at all regarding what the government has seen and not liked, it is hard to know whether DL and this issue is even on the list.
And there really have not been settlements with no admission of guilt regarding fare disclosures. either the DOT has fined carriers and the carriers have said they would implement changes to fix the allegation or rules have been changed because the DOT has not liked the level of rules that have existed.