First of all, you registered here less than 3 months ago. Serthon has played here for 2 years. So you see there is quite a difference between your "completely clean records."
Now, sorry you didn't get verbal guidance. Feel free to appeal. Did you admit wrong doing at the time of the report / investigation? Did you apologize? Did you offer to refund any losses on the spot after taking the time to look at it from others point of view? If you had and you still got punished i'd definitely like to see that in an appeal!
Here are examples of "simple users" receiving verbal guidance and other players having the common decency to agree to verbal guidance for DM within just the time you've played here. If you'd like, we have 2 more years of examples. I'd also like to point out the third example is Serthon himself giving this same type of punishment to an average player. So in a sense, you're asking for him to be treated harsher than he treats you and other players.