It turns out that the "Pressing AKEY to deselect all objects still

leaves one object center pink" bug was actually designed by somebody
to mark the active object (which need not necessarily be selected).
I've added a couple of source comments to explain this so the next
person trying to fix this doesn't bother.

source/blender/src/drawobject.c

@@ -3607,6 +3607,9 @@ void draw_object(Base *base)
 			}
 			else {
 				if(base->flag & SELECT) rect= rect_sel;
+				/* The center of the active object (which need not 
+				 * be selected) gets drawn as if it were selected
+				 */
 				else if(base==(G.scene->basact)) rect= rect_sel;
 				else rect= rect_desel;
 			}

source/blender/src/space.c

@@ -633,7 +633,13 @@ void winqread3d(unsigned short event, short val, char ascii)
 					}
 					else {
 						if(G.f & G_FACESELECT) deselectall_tface();
-						else deselectall();
+						else {
+							/* by design, the center of the active object 
+							 * (which need not necessarily by selected) will
+							 * still be drawn as if it were selected.
+							 */
+							deselectall();
+						}
 					}
 				}
 				break;