Cross-posting to happy thoughts.
Just received a letter from [financial institution]. After sending a small packet of information out explaining things in fairly exhaustive detail, they’ve written back: m’s account is cleared. The exact language is “a deletion occurred as a result of insufficient evidence to conclude account ownership liability” - which, I have no idea what “a deletion occurred” is supposed to mean - but the bottom line is, [financial institution] says it’s contacting all credit reporting agencies to request it be deleted from m’s credit report.