Note: In general, full-time employees with employer coverage available that meets specified requirements are not eligible for premium subsidies, unless the employee would have to pay more than 9.8% of income for the employer-provided coverage.
Which is actually a max based on a family plan. If you scroll down, it's explained:
For income up to: 400% of poverty
Maximum family payment of: 9.8% of income
It has nothing to do with the 8 percent limit for exemption on an individual income.
And even so, people will still be able to buy as much insurance as they want to.