I viewed a refund interaction for an ACH transaction on a constituent record and the "Solicitor" field shows "Task Admin". I ran a ReportWriter report and the field for who processed the refund is blank or shows the "Task Admin".
If an ACH transaction comes back as unable to be settled, a task deletes the transaction out of the system. Note that the deletion looks like a refund; the only difference being between a deletion and a refund is that no money changes hands for a deletion. So when an ACH transaction comes back unable to settled that means the transaction was not funded so it is automatically deleted from the system. In ReportWriter reports, the "Refund By" column will show blank for the deletions.