It’s mostly with private student loans that people go completely underwater in the US
Only if you switch to the income-based repayment plan, which has to be reverified every year.
Prior to December 2020 taxes were owed on forgiven debt the year it was finally forgiven. Which could be very harsh if the debt was large. https://www.nerdwallet.com/article/loans/student-loans/how-t...
I'm not sure how it works in the UK, but in the US at least this extra debt is negatively factored into things like credit scores.
And regardless of the payment, it takes a bite out of income. I couldn't afford a PPACA medical plan for a few reasons, but partly because I was paying for loans. None of these repayment plans factor in affordability for the payee, they are a straight percentage of income basis or treat the payee as some sort of national average in terms of expected affordability.
The debt is of course on your credit report, but if you are making payments, more likely than not it's going to be beneficial, as young people are unlikely to have other debts that are considered "old". My own student loans carried the "age of credit" criteria on my credit report for a while.
They are a percentage of income, but that is no different than the UK version. And to be fair to IBR, it's more nuanced that that - the income cutoff for the percentage varies state-by-state (so, someone in New York has a much higher cutoff than someone in Arkansas).