With radio not working, why it is more important to stay away from exactly class D airspace?
I think you are mis-interpreting the answer, you should remain outside Class-D until the flow of traffic can be acertained. If you lose comms outside of a Class-B or Class-C, you should not enter that airspace, instead divert to a Class-D or E airport if possible. If you are already inside the B/C airspace, continue, but don't enter. Class-A is different, as it is not surrounding airports and you can fly IFR after you've gotten your clearance with lost comms.

The original question links to the AIM, Chapter 4, Section 2-13, read that and see if it clears things up.