That is to say, as long as a mod doesn't make it into a RD thread anyways.
They typically ask the OP first. As far as I can tell, the thread is made RD when the alternative is locking it due to the plethora of spam and unproductive responses. So then you have a choice: go with the non-RD thread, in which case there isn't any because it got locked (and would have gotten locked anyways regardless of the Red Diamond Initiative); or go with the RD thread.
Let me show it under another light : why moderation should have different standards ?
Lax standards are applied when you want a thread that is lighthearted and contains comments diverse in their relevance and usefulness. Stricter standards are applied when you want to cut away all of that and ensure that what remains is a proper form of discussion and discourse.
The result is that you have the option of setting increased moderation standards in order to increase the likelihood of more serious discussion.