move Rationale below Specification because FLUFL

Author: gpshead

peps/pep-0830.rst

@@ -96,17 +96,6 @@ traces from other services or even logs from the program itself to build a
 complete picture.
 
 
-Rationale
-=========
-
-The timestamp is stored as a single ``int64_t`` field in the ``BaseException``
-C struct, recording nanoseconds since the Unix epoch.  This design was chosen
-over using exception notes (:pep:`678`) because a struct field costs nothing
-when not populated, avoids creating string and list objects at raise time, and
-defers all formatting work to traceback rendering.  The feature is entirely
-opt-in and does not change exception handling semantics.
-
-
 Specification
 =============
 
@@ -184,6 +173,17 @@ Third-party projects are **not** expected to support running their tests with
 timestamps enabled, and we do not expect many projects would ever want to.
 
 
+Rationale
+=========
+
+The timestamp is stored as a single ``int64_t`` field in the ``BaseException``
+C struct, recording nanoseconds since the Unix epoch.  This design was chosen
+over using exception notes (:pep:`678`) because a struct field costs nothing
+when not populated, avoids creating string and list objects at raise time, and
+defers all formatting work to traceback rendering.  The feature is entirely
+opt-in and does not change exception handling semantics or performance.
+
+
 Backwards Compatibility
 =======================
 
@@ -198,7 +198,8 @@ dictionary.  Older Python versions unpickle these correctly via
 ``__setstate__``.  Always emitting the 3-tuple form (with a zero timestamp)
 would simplify the logic, but was avoided to keep the pickle output
 byte-identical when the feature is off and to avoid any performance impact
-on the common case.
+on the common case.  As much as this author prefers simpler code, it felt
+riskier to have exception pickles all increase in size as a default behavior.
 
 
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