Merge pull request #4048 from puchik/shading-language-vocabulary-grammar

Formalize language and improve grammar in "Shading Language"

tutorials/shading/shading_reference/shading_language.rst

@@ -186,10 +186,11 @@ Using lower precision for some operations can speed up the math involved (at the
 This is rarely needed in the vertex processor function (where full precision is needed most of the time),
 but is often useful in the fragment processor.
 
-Keep in mind that some architectures (mainly mobile) benefit a lot from this, but are also restricted
-(conversion between precisions has a cost). Please read the relevant documentation on the target architecture
-to find out more. In all honesty though, mobile drivers are buggy, so, to stay out of trouble, make simple
-shaders without specifying precision unless you *really* need to.
+Some architectures (mainly mobile) can benefit significantly from this, but
+there are downsides such as the additional overhead of conversion between
+precisions. Refer to the documentation of the target architecture for further
+information. In many cases, mobile drivers cause inconsistent or unexpected
+behavior and it is best to avoid specifying precision unless necessary.
 
 Arrays
 ------