hey y'all i just found a workaround for this!
open the information-window of your user-folder, and then under "name" rename it to the name you want to have in your finder-sidebar.
your folder then gets the generic folder symbol, but still doesn't display your name properly. so move this folder out of the sidebar, and via finder/preferences/sidebar reactivate your user-folder in the sidebar..
and woo, there you go =)