[dom0]

A good formal reference uses way-over-the-top wording, a bad formal reference basically just says "ok". This is due to German law not allowing for "the employee sucks", nor allows it to use "code-speak" (it was often used in the past, but a bunch of lawsuits pretty much removed it and most HR people don't even try to push for it any more).

Good: "Mr. X's technical competence is excellent. He solved difficult technical challenges quickly and correctly. His performance at our company exceeded our expectations."

Bad: "Mr. X handled assigned tasks adequately."

A long reference almost always means it is good. If it's longer than two pages, it's almost certainly excellent.

In Germany, employees can request a "simple" reference, which basically just certifies employment and does not contain any judgement. What I described above is a "qualified" reference; usually it is seen as a bad sign to produce just a "simple" reference and not a "qualified" reference.