If I'm a single shareholder/owner and employee of a C Corporation, am I limited from taking any deductions due to being a highly-compensated employee (due to share ownership)?
My situtation is similar to yours and my experiences has shown the IRS treats you the same as any other employee. Same tax forms, same rules when you file.
The tax form for the C Corp requires you to list "officer's salaries" separately, but it is still viewed as a payroll expense. If you had employees their salaries would be in another category, but again part of payroll expense.