> The difference here is that professional translators often have professional training.

You'd be surprised. What you described here for programmers is true for translators as well, and probably for many other specialities in which the ability to deliver the result is more important than any documents certifying that you've had a formal training for how to deliver those results. In case of translators — found an agency? Check. Passed an interview with a test? Check. You are good to go.