It's not a nitpick, but also that newsletter is not indicative of GOG being a Nazi organization. The idea that they specifically decided to advertise a new game based on Slavic mythology specifically so that they could send a mass advertisement to half their user base intentionally using Nazi symbolism is wild. It is much more likely that some marketing dimwit Googled "Slavic runes," and copied some random ones from the first site they found.
Screenshot of the first result for "slavic emoji" on google
It's one data point, not a pattern. Definitely something to watch out for, but there's literally nothing else in the history of the company to suggest that they have any white supremacist tendencies