If John has no equity he can ask the IRS to discharge the lien and allow the sale.  

However, generally speaking, a Bankruptcy Trustee can declare a specific debt as non-dischargeable through bankruptcy due to "Fraud" on the part of the Debtor.

He was a sergeant in the United States Marine Corp before being honorably discharged.

That will give any papers filed against that owner/property (like a mortgage) Anything that has been discharged (like a mortgage) should also be recorded.

Since I filed for a chapter 7 bankruptcy in May of 2014 and it was discharged in August of 2014.

It occurred to me that a couple of years ago I created a bathroom in a lake house we had and I had to put in a rear discharge toilet (sounds redundant) to avoid cutting into the slab by drilling a hole through a cinder block wall. 

I am a recent honorably discharged vet (Navy) and I work a 6pm-6am 12 hour shift w-2 job. 

In general, How is DTI measured in relation to discharged debts still being paid but not reaffirmed?

The mortgage debt can be discharged as a function of the plan which means the debtor no longer personally owes on the debt.  

For VA home loan purposes, a veteran is a person who has served or is currently serving on active duty in the United States Military or Coast Guard and who was discharged or released from active duty under conditions other than dishonorable.