User blog comment:Jopjopjop/Volume 19 Spoilers/@comment-24.64.83.13-20141121165307/@comment-1359322-20141122001301

I don't think Issei can kill Diehauser. Supposing even if Issei can kill Diehauser, until Diehauser is proven as a real traitor, even if Diehauser did kill the Phenex siblings, it would just be viewed as a Rating Game accident death. And Issei killing Diehause out of personal grudge would just make Issei a murderer in the eyes of others, if they can't prove Diehauser is a traitor.