Apply suggestions from code review by @hugovk

Co-authored-by: Hugo van Kemenade <1324225+hugovk@users.noreply.github.com>

Author: astrofrog

peps/pep-0771.rst

@@ -74,7 +74,7 @@ Rationale
 =========
 
 A number of possible solutions have been extensively and vigorously discussed by
-the community for several years, including in `this DPO threadq
+the community for several years, including in `this DPO thread
 <https://discuss.python.org/t/adding-a-default-extra-require-environment/4898/38>`__
 as well as in numerous issues and pull requests. The solution that will be
 presented below:
@@ -128,7 +128,7 @@ produce the example ``Default-Extra`` entries presented in the previous section
 
     [project]
     default-optional-dependencies = [
-        "recommended"
+        "recommended",
     ]
 
 and:
@@ -150,7 +150,7 @@ If extras are explicitly given in a dependency specification, the default
 extras are not installed. Otherwise, the default extras are used.
 
 For example, if a package
-defines a ``extra1`` default extra as well as a non-default ``extra2``
+defines an ``extra1`` default extra as well as a non-default ``extra2``
 extra, then if a user was to install the package with::
 
     pip install package
@@ -354,7 +354,7 @@ properly document the options available to users in terms of installation.
 Reference Implementation
 ========================
 
-The following branch contains a modified version of the `flit
+The following branch contains a modified version of the `Flit
 <https://flit.pypa.io/en/stable/>`_ package which recognizes the
 ``default-optional-dependencies`` key in ``pyproject.toml`` and adds the
 relevant ``Default-Extra:`` metadata to the build package:
@@ -372,15 +372,15 @@ test out different scenarios and use cases described in this PEP:
 
 https://github.com/astrofrog/pep-771-demo
 
-The implementations above are proof-of-concepts at this time, do not include any
+The implementations above are proofs-of-concept at this time, do not include any
 tests or documentation in the respective packages, and the existing changes have
 not yet been reviewed by the relevant maintainers. Nevertheless, they are
 functional enough to allow for interested maintainers to try these out.
 
 Rejected Ideas
 ==============
 
-Syntax for unselecting extras
+Syntax for deselecting extras
 -----------------------------
 
 One of the main competing approaches was as follows: instead of having defaults
@@ -431,7 +431,7 @@ The idea would be that dependencies installed as part of the 'empty' extras
 would only get installed if another extra was not specified. An implementation
 of this was proposed in https://github.com/pypa/setuptools/pull/1503, but it
 was found that there would be no way to make this work without breaking
-compatibility with existing usage. For example, packages using setuptools via
+compatibility with existing usage. For example, packages using Setuptools via
 a ``setup.py`` file can do::
 
     setup(
@@ -441,7 +441,7 @@ a ``setup.py`` file can do::
 
 
 which is valid and equivalent to having ``package_a`` being defined in
-``install_requires``, so changing the meaning of the empty string requires would
+``install_requires``, so changing the meaning of the empty string would
 break compatibility.
 
 In addition, no other string (such as ``'default'``) can be used as a special