it would be unethical to lie about the candidate's skills and personality, misleading prospective employers.

All employers can ask that with zero liability.

Employers are NOT restricted in making factual comments on former employers. They are liable only if they make knowingly false statements.

Prospective employers can ask about your former job, too.

Prospective employers are seeking qualified applicants. Regardless if your skills were from a traditional source or online training, the bottom line will be if you qualified and will be an asset to the company.

No federal or state statutes prevent employers from ASKING anything. Very few laws restrict employers from ANSWERING prospective employers questions.