printf %b is POSIX, so move that suggestion into the Rationale section

SC2059.md

@@ -26,8 +26,6 @@ The first printf writes `Unit test coverage: 96%`.
 
 The second writes ``bash: printf: `\': invalid format character``
 
-### Exceptions
-
 Sometimes you may actually want to interpret data as a format string, like in:
 
 ```sh
@@ -35,13 +33,24 @@ octToAscii() { printf "\\$1"; }
 octToAscii 130
 ```
 
-In Bash, Ksh and BusyBox, there's a `%b` format specifier that expands escape sequences without interpreting other format specifiers: `printf '%b' "\\$1"`. In POSIX, you can instead [[ignore]] this warning.
+In this case, use the `%b` format specifier that expands escape sequences without interpreting other format specifiers:
 
-Other times, you might have a pattern in a variable:
+```sh
+octToAscii() { printf '%b' "\0$1"; }
+octToAscii 130
+```
+
+### Exceptions:
+
+Sometimes you might have a pattern in a variable:
 
 ```sh
 filepattern="file-%d.jpg"
 printf -v filename "$filepattern" "$number"
 ```
 
-This has no good rewrite. Please [[ignore]] the warning with a [[directive]].
+This has no good rewrite. Please [[ignore]] the warning with a [[directive]].
+
+### Related resources:
+
+* https://pubs.opengroup.org/onlinepubs/9699919799.2018edition/utilities/printf.html