I'm Zyirkon, an author on the German Wikipedia. I work almost exclusively in the field of chemistry, primarily creating and maintaining structural formulas. I'm also involved in checking incoming chemical articles, maintaining a lot of small stuff, and occasionally creating a new article.
On Commons, I almost exclusively upload structural formulas and correct file descriptions and licenses as soon as I notice them.
If you discover an error, please let me know on my user talk; I can usually correct errors within a few hours.