Debt Collectors and Trademark Infringement:

A creditor (credit card company, bank, physician, etc.) assigns or sells a debt for collections to a third party debt collector or debt buyer, the debt collector further assigns the debt to a law firm. The law firm is representing the 3rd party debt collector, but uses the original creditors name (trademarked name) in filing suit.
It is Trademark Infringement Folks
The law firm is not directly representing the original creditor and doesn’t have direct consent of the creditor to file suit (remember they were employed by the third party assignee or debt buyer).
This is trademark infringement and companies reputations and names are being tarnished by misuse of their names. Not only that it is dilution of their brand and causing much consumer confusion.
If you look at it another way these third party to a third party law firms are using the companies tradename to benefit financially (used in commerce).

Hmmm. Well, speaking in the abstract, if a trademark licensee says “I am trademark owner” as opposed to “I am trademark owner’s licensee,’ that may be problematic (however there is such a thing as a trading name license). Consumer debt colection is heavily regulated – there may well be state regulations governing how the debt collector identifies itself that cover this issue. However here the article is suggesting that a law firm is mis-identifying its client. You would likely want to go the professional responsibility statute to analyze that one first.
However, it seems that the law firm HAS to identify the trademark owner is some way. How else would the consumer know which debt is being collected? (as to whether a law firm can threaten suit when it has not been authorized to do again is not a trademark issue).