Article linked elsewhere seems to indicate it didn't go to German users because the German QA team found the issue before it was sent, but due to an internal communication breakdown the issue didn't make it back to the international team before the emails had already been sent. GOG immediately apologized for the mistake and changed their internal processes to catch these types of mistakes sooner.

It very much reads like an honest mistake, and even then it only impacted a subset of GOG users because it's entirely dependent on the font used to render the email subject. The actual Unicode character used was a curved S (a letter from the Greek character set), but certain fonts render it looking more like the infamous SS symbol.