Personally I consider these PMs are ADVERTISING AND SPAM. Ive had one of these PMs for the Azure Version and I think a giant flame war is going to begin if this keeps happening. I thought this was not allowed and would be punished, Ive seen nothing. More and more of these spam PMs are occuring it is just plain selfish. I know you think Im probably overreactig here it is just going to lead into disaster with all different bad stuff, lots breaking the rule list. Theres gonna be lots of aruguments and riots over the forum, what will happen then? I know this is gonna lead to lots of disagreements but I wanted to show what I think and not having to follow other non - mod/admin statements otherwise if told by them.
Back to your problem, I think it is impossible to change it otherwise hacking which is obviously not recommended. Maybe like NN said about the Admin CP if lots of people ask kindly to WPM to change with a backup statement.