The generated accumulated commit message is language and git configuration independent.
This gives unstable test results, as well as users can not always be sure that they get the expected accumulated commit message if build slaves have different language and locale settings.
Currently best found solution is to enforce english locale settings in the accumulated commit message. Currently there is none, thus it is build environment dependent.
It does not affect the squash commit message, as this is generated by Git and seems to have defaults that matches english.