Is this person's real full name known?
Based on thread on local board, his name is "Bambang". But it's not specified whether it's just first name or full name.
But about the legality, their family, spouse or friend have no legal obligation the debt in most cases. It's different case if that person wish to keep asset which isn't fully paid yet or cosigned a loan with the deceased one.
Any debt is usually passed on spouse or other family members
Not really, here's what investopedia say (i don't know other reliable source).
In general, no one else is responsible for repaying your debt after you die, with a few major exceptions:
Cosigner: If you had applied for a loan with a cosigner, that person is typically obligated to repay the debt.
Joint account holders: If you had a joint account, such as a credit card shared with a family member, the joint account holder must repay the debt.
Spouse: In some states, spouses are required to repay some forms of debt. In community property states, the surviving spouse may have to use community property to repay their partners debt. Community property states include Alaska, Arizona, California, Idaho, Louisiana, Nevada, New Mexico, Texas, Washington, and Wisconsin.
And in some country, there's also option to reject
all inheritance to avoid paying deceased debt.
but I have no idea how this would apply for coins someone borrowed in bitcointalk forum.
Legality of this is not cleat in many jurisdictions, and people could also remain private, not connecting bitcointalk account with their real identity.
I have no idea either, especially when lender and borrower live on different country.