I would hire anyone regardless of the source of their training as long as they are capable of demonstrating proficiency, a firm grasp on the core concepts and a willingness and determination to learn.
What metrics / standards would you use to vet a potential hire? (someone with no previous professional work experience). Personal work portfolio, strictly interview questions? The benefit of a degree is an implicit sign off from a reputable institution. How would you think about replicating that comfort for someone who is self taught?
- heavy interviewing with plenty of tests and several (3-6 people) giving written feedback on the candidate in the form of 5 points rating on lots of skills
- hire on gut feeling
mixed in various amounts.
In my case, a diploma/certificate doesn't make me feel better. I've seen plenty of incompetents with a diploma, so I don't take it at face value. Testing worked best for me.
A diploma/certificate also doesn't tell you anything about the candidate's work style/attitude. A hire with a bad attitude is much more toxic than a hire that lacks technical skills.