docs for canonicalization

NEWS.md

@@ -24,6 +24,12 @@ This section lists changes that do not have deprecation warnings.
   * `broadcast` now handles tuples, and treats any argument that is not a tuple
     or an array as a "scalar" ([#16986]).
 
+  * Fullwidth and halfwidth characters are now considered equivalent in
+    identifiers, and certain Greek-like Unicode characters
+    (µ "micro" and ɛ "latin epsilon") are considered equivalent to
+    the corresponding Greek characters, for ease of input.  `\varepsilon`
+    now tab-completes to U+03B5 (greek small letter epsilon).  ([#19464])
+
 Library improvements
 --------------------
 

doc/manual/variables.rst

@@ -134,6 +134,15 @@ statements:
     ERROR: syntax: unexpected "="
      ...
 
+Some Unicode characters are considered to be equivalent in identifiers.
+"Fullwidth" versions of ASCII and other symbols are treated as equivalent
+to the ordinary (halfwidth) versions, to simplify Julia code entry in
+some Asian languages.  The Unicode characters ``ɛ`` (U+025B: Latin small letter open e)
+and ``µ`` (U+00B5: micro sign) are treated as equivalent to the corresponding
+Greek letters, because the former are easily accessible via some input methods.
+Different ways of entering Unicode combining are treated as equivalent
+(specifically, Julia identifiers are NFC-normalized).  These canonicalizations
+also occur whenever a Julia ``Symbol`` is created.
 
 Stylistic Conventions
 =====================