Proposed resolution:

This wording is relative to N5032.

1. Modify [linalg.scaled.scaledaccessor] as indicated:

   namespace std::linalg {
     template<class ScalingFactor, class NestedAccessor>
     class scaled_accessor {
     public:
       using element_type =
         const decltype(declval<const ScalingFactor&>() * 
                        typename declval<NestedAccessor::element_type>(
                           declval<typename NestedAccessor::reference>()));
       […]
     };
   }
   

2. Modify [linalg.conj.conjugatedaccessor] as indicated:

   namespace std::linalg {
     template<class NestedAccessor>
     class scaled_accessor {
     public:
       using element_type =
         const decltype(conj-if-needed(
                          typename declval<NestedAccessor::element_type>(
                            declval<typename NestedAccessor::reference>())));
       […]
     };
   }
   

The scaled_accessor defines element_type as const decltype(declval<ScalingFactor>() * ...), but its access returns (scaling_factor() * ...), where scaling_factor() returns const ScalingFactor&.

Furthermore, both scaled_accessor and conjugated_accessor's access construct NestedAccessor::element_type via nested-accessor.access(p, i), but this may not be well-formed.