The loopholes are well known at this point. They keep renewing loans until they die, then it's tax-free after death. It's called Buy-Borrow-Die.
Buy-Borrow-Die resets the basis for capital gains tax, but then there's estate tax when the money gets passed on (exemption is only $15 million, trivial to billionaires).
Taxed on repaying a loan?
No, taxed when you earn the money that repays the loan. Income tax, capital gains taxes, dividend taxes, estate taxes, etc... However the money was acquired to repay the loan, a tax was applied.
Which is pendantically and functionally very different from the implied tax on repayment.
Maybe you didn't read it properly, I said taxed "on the income" then specified that's the money "used to pay it back".
Income has a specific definition if you want to be pedantic, and types of income are always taxed.
I read it properly but "the implied tax on repayment" was referring to lovecg's comment.