Copy edit Section 2 intro, fixes #302. (#322)

* Copy edit Section 2 intro, fixes #302.

Moves extra text about context to a Context section in the
Common Concepts appendix.

* Apply suggestions from code review

Co-authored-by: Jeffrey Yasskin <[email protected]>

---------

Co-authored-by: Jeffrey Yasskin <[email protected]>

index.html

@@ -1024,17 +1024,13 @@
 
 # Principles for Privacy on the Web
 
-As indicated above, different [=contexts=] require different principles. This section describes a set
-of principles designed to apply to the Web [=context=] in general. The Web is a big place, and we
-fully expect more specific [=contexts=] of the Web to add their own principles to further constrain
-[=information flows=].
-
-To the extent possible, [=user agents=] are expected to enforce these principles. However, this is not
-always possible and additional enforcement mechanisms are needed. One particularly salient issue
-is that a [=context=] is not defined in terms of who owns or controls it. Sharing
-[=data=] between different [=contexts=] of a single company is just as much a [=privacy violation=] as
-if the same data were shared between unrelated [=actors=].
+This section describes a set of principles designed to apply to the web
+[=context=] in general. Specific [=contexts=] on the web may need more
+constraints or other considerations. In time, we expect to see more specialized
+privacy principles published, for more specific [=contexts=] on the web.
 
+These principles should be enforced by [=user agents=]. When this is not possible,
+additional enforcement mechanisms are needed.
 
 ## Identity on the Web {#identity}
 
@@ -2134,9 +2130,15 @@
 are people in some situations of intellectual or psychological impairment, are
 refugees, etc.
 
+## Contexts {#context}
+
 A <dfn>context</dfn> is a physical or digital environment in which [=people=] interact with other
 [=actors=], and which the [=people=] understand as distinct from other [=contexts=].
 
+A [=context=] is not defined in terms of who owns or controls it. Sharing
+[=data=] between different [=contexts=] of a single company is
+a [=privacy violation=], just as if the same data were shared between unrelated [=actors=].
+
 ## Server-Side Actors {#parties}
 
 An <dfn>actor</dfn> is an entity that a [=person=] can reasonably understand as a single "thing"