In the Blender 2.77 release notes was this dramatic announcement:
"Better threading handling: Blender is now massively multi-threaded."
After that I experienced a dramatic increase of speed, the same blistering fast speed that I can get in MMD. Based on that experience, I deduced that MMD's blistering fast speed probably comes from multi-threading.
In a later version of Blender, maybe 2.79, I remember that it was announced that Blender multi-threading was defective and had been removed from Blender. Since then I have been limping along with the same old Blender slow speed.
The Blender release notes are here: https://en.blender.org/index.php/Dev:Ref/Release_Notes
I just looked at these release notes and I could not find the announcement of multi-threading being removed from Blender. Does anyone know what the situation is with multi-threading in Blender? I miss that increase of speed.