Clarify language and fix minor wording issues

Author: ZeroIntensity

peps/pep-0828.rst

@@ -108,8 +108,8 @@ in asynchronous generators:
 2. https://discuss.python.org/t/47050
 3. https://discuss.python.org/t/66886
 
-Additionally, this design decision has `come up
-<https://stackoverflow.com/questions/47376408>`__ on Stack Overflow.
+Additionally, users have `questioned <https://stackoverflow.com/questions/47376408>`__
+this design decision on Stack Overflow.
 
 
 Subgenerator delegation is useful for asynchronous generators
@@ -122,11 +122,11 @@ item. This comes with a few drawbacks:
 1. It obscures the intent of the code and increases the amount of effort
    necessary to work with asynchronous generators, because each delegation
    point becomes a loop. This damages the power of asynchronous generators.
-2. :meth:`~agen.asend`, :meth:`~agen.athrow`, and :meth:`~agen.aclose`,
+2. :meth:`~agen.asend`, :meth:`~agen.athrow`, and :meth:`~agen.aclose`
    do not interact properly with the caller. This is the primary reason that
    ``yield from`` was added in the first place.
 3. Return values are not natively supported with asynchronous generators. The
-   workaround for this it to raise an exception, which increases boilerplate.
+   workaround for this is to raise an exception, which increases boilerplate.
 
 
 Specification