2.2.7 [XML] Section 4.2, Entity Declarations


The specification states:

 The Name identifies the entity in an entity reference or, in the case of an 
 unparsed entity, in the value of an ENTITY or ENTITIES attribute. If the same 
 entity is declared more than once, the first declaration encountered is binding; 
 at user option, an XML processor MAY issue a warning if entities are declared 
 multiple times.

IE9 Mode, IE10 Mode, IE11 Mode, and EdgeHTML Mode (All Versions)

No warning is issued if entities are declared multiple times.