Warn users against dangerous macros.
Also, mark EIGEN_DEFAULT_TO_ROW_MAJOR as internal (see also bug #422).
diff --git a/doc/I15_StorageOrders.dox b/doc/I15_StorageOrders.dox
index 6b56ca8..7418912 100644
--- a/doc/I15_StorageOrders.dox
+++ b/doc/I15_StorageOrders.dox
@@ -60,10 +60,8 @@
\c ColMajor, then it is stored in column-major order. This mechanism is used in the above Eigen program to
specify the storage order.
-If the storage order is not specified, then Eigen normally defaults to storing the entry in column-major
-order. This is also the case if one of the convenience typedefs (\c Matrix3f, \c ArrayXXd, etc.) is
-used. However, it is possible to change the default to row-major order by defining the
-\c EIGEN_DEFAULT_TO_ROW_MAJOR \ref TopicPreprocessorDirectives "preprocessor directive".
+If the storage order is not specified, then Eigen defaults to storing the entry in column-major. This is also
+the case if one of the convenience typedefs (\c Matrix3f, \c ArrayXXd, etc.) is used.
Matrices and arrays using one storage order can be assigned to matrices and arrays using the other storage
order, as happens in the above program when \c Arowmajor is initialized using \c Acolmajor. Eigen will reorder
