docs for canonicalization

NEWS.md

@@ -55,6 +55,7 @@ This section lists changes that do not have deprecation warnings.
 
   * `broadcast` now treats `Ref` (except for `Ptr`) arguments as 0-dimensional
     arrays ([#18965]).
+
   * `broadcast` now handles missing data (`Nullable`s) allowing operations to
     be lifted over `Nullable`s, as if the `Nullable` were like an array with
     zero or one element. ([#16961]). Note that many situations where `Nullable`
@@ -76,6 +77,12 @@ This section lists changes that do not have deprecation warnings.
 
   * `quadgk` has been moved from Base into a separate package. ([#19741])
 
+  * Fullwidth and halfwidth characters are now considered equivalent in
+    identifiers and code, 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/src/manual/variables.md

@@ -108,6 +108,15 @@ 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).
+
 ## Stylistic Conventions
 
 While Julia imposes few restrictions on valid names, it has become useful to adopt the following