I continue to respectfully disagree. Once upon a time, the second mortgage was a secured interest. The code (which I have not bothered to read) says that interest payments against that secured interest are deductible. Since a second mortgage is presumed to be an arm's length transaction, it remains a secured interest until an overt act intervenes, e.g. sale of property or foreclosure.
My position remains that the IRS would lose such a denial of an interest deduction all the way from the local Tax Court and up to Johnny and Supremes BECAUSE an overt act (as mentioned above) has not intervened.
I seriously doubt that the Supremes would even hear an appeak from the IRS.
Dick