Use "impl-detail" directive where applicable.
diff --git a/Doc/reference/simple_stmts.rst b/Doc/reference/simple_stmts.rst
index 3886601..b9cdd91 100644
--- a/Doc/reference/simple_stmts.rst
+++ b/Doc/reference/simple_stmts.rst
@@ -219,9 +219,11 @@
the length of the assigned sequence, thus changing the length of the target
sequence, if the object allows it.
-(In the current implementation, the syntax for targets is taken to be the same
-as for expressions, and invalid syntax is rejected during the code generation
-phase, causing less detailed error messages.)
+.. impl-detail::
+
+ In the current implementation, the syntax for targets is taken to be the same
+ as for expressions, and invalid syntax is rejected during the code generation
+ phase, causing less detailed error messages.
WARNING: Although the definition of assignment implies that overlaps between the
left-hand side and the right-hand side are 'safe' (for example ``a, b = b, a``
@@ -946,9 +948,11 @@
parameters or in a :keyword:`for` loop control target, :keyword:`class`
definition, function definition, or :keyword:`import` statement.
-(The current implementation does not enforce the latter two restrictions, but
-programs should not abuse this freedom, as future implementations may enforce
-them or silently change the meaning of the program.)
+.. impl-detail::
+
+ The current implementation does not enforce the latter two restrictions, but
+ programs should not abuse this freedom, as future implementations may enforce
+ them or silently change the meaning of the program.
.. index::
statement: exec