1) It does not help the German people if green energy is generated in Norway or someone puts up a solar panel in the Sahara if they get to breathe emissions from coal power plants.
2) Any overly complex scheme is likely to be gamed. Any German household can order "Öko-Strom". I don't believe for a second that enough real "Öko-Strom" is available to fulfil that demand in a legitimate manner.
In (2) you say that the scheme is likely to be gamed. Can you elaborate on how that would look like? Does this "Occam's razor" necessarily mean that only simple laws are effective?
Also in (2) you claim that there is not enough real green energy available to satisfy the demand. This is obviously true but this means that the demand creates an incentive for companies to produce green energy wherever possible.
Overall what this system really provides is an option for consumers to optionally subsidize green energy producing companies and so far I have not really heard of any concrete case in which this system has been gamed. Do you know any?
Go and continue to believe that the world is just, no gaming of the system occurs, as clueless and highly paid A12-A16 civil servants [1] have told you in school.
[1] German teachers are paid well in return for their indoctrination.
Anyway, the article's argument is that the certificates for renewable energy are created in e.g. Norway and Switzerland where it is easy to produce cheap hydropower which cannot be transported to Germany. Meanwhile the Norwegian and Swiss do not buy energy with certificates because they "know" that their energy is clean.
This is indeed true and a valid argument. However Norway and Switzerland produce only a finite amount of these certificates. If demand for certified green energy does not exceed this supply then this is simply a sign that not enough people are willing to pay extra for certified green energy which is regrettable but not a fault of this system.
I'm not surprised by the low quality of discussion.