--text follows this line--

Attempting to bind unicode characters (e.g. \u111E) to keys in a minor mode with syntax like
  (define-key my-test-mode-map (kbd "c") "\u221E")
usually works. In this case, C-h k c shows

c runs the command #<string CB7> (found in my-test-mode-map), which is
a keyboard macro.
It is bound to c.
Macro: M-\20636
Keyboard macro.

However the same syntax fails for some characters (so far I've noticed this for \u00B0 to \u00B6 but there will be more) e.g
after (define-key my-test-mode-map (kbd "a") "\u00B2") C-h k shows

a runs the command #<string B6B> (found in my-test-mode-map), which is
a keyboard macro.
It is bound to a.
Macro: M-2
Keyboard macro.

and the effect of pressing "a" is to invoke command-digit-argument rather than insert the required character

A workaround is to use a lambda expression to bypass whatever emacs is doing when processing the unicode character, e.g.
  (define-key my-test-mode-map (kbd "b") (lambda () (interactive) (insert "\u00B2")))

and then this does insert the character (superscript 2) when "b" is pressed.

To replicate:

1. run emacs -Q

2. paste the following into the scratch buffer:

;; This buffer is for text that is not saved, and for Lisp evaluation.
;; To create a file, visit it with ‘C-x C-f’ and enter text in its buffer.

(progn
  ;; 1. Explicitly create the keymap variable and initialize it.
  (defvar my-test-mode-map (make-sparse-keymap)
    "Keymap for `my-test-mode'.")

  ;; 2. Define the minor mode, telling it to use our explicitly created map.
  (define-minor-mode my-test-mode
    "A test minor mode."
    :global t
    :lighter " my-test"
    :keymap my-test-mode-map
    )

  ;; 3. Define keys on the explicitly created and linked map.

;; normal bind fails at least for characters in range \u00B0 to \u00B6, but probably more, e.g. \u00B2
  (define-key my-test-mode-map (kbd "a") "\u00B2")

  ;; workaround is to use a lambda
  (define-key my-test-mode-map (kbd "b") (lambda () (interactive) (insert "\u00B2")))

; normal bind does succeeds with other characters I've tried so far, e.g. \u221E
  (define-key my-test-mode-map (kbd "c") "\u221E")

  ;; 4. Enable the minor mode.
  (my-test-mode 1)
  )
 
===

This creates a new mode "my-test-mode" with the key maps and puts it into effect. Then try pressing a, b and c.

(acknowledgements to assistance from gemini 2.5 on all this!)


In GNU Emacs 30.1 (build 2, x86_64-w64-mingw32) of 2025-02-23 built on
 AVALON
Windowing system distributor 'Microsoft Corp.', version 10.0.26100
System Description: Microsoft Windows 10 Pro (v10.0.2009.26100.4061)

Configured using:
 'configure --with-modules --without-dbus --with-native-compilation=aot
 --without-compress-install --with-tree-sitter CFLAGS=-O2
 prefix=/g/rel/install/emacs-30.1'

Configured features:
ACL GIF GMP GNUTLS HARFBUZZ JPEG LCMS2 LIBXML2 MODULES NATIVE_COMP
NOTIFY W32NOTIFY PDUMPER PNG RSVG SOUND SQLITE3 THREADS TIFF
TOOLKIT_SCROLL_BARS TREE_SITTER WEBP XPM ZLIB

(NATIVE_COMP present but libgccjit not available)

Important settings:
  value of $LANG: ENG
  locale-coding-system: cp1252

Major mode: Lisp Interaction

Minor modes in effect:
  tooltip-mode: t
  global-eldoc-mode: t
  eldoc-mode: t
  show-paren-mode: t
  electric-indent-mode: t
  mouse-wheel-mode: t
  tool-bar-mode: t
  menu-bar-mode: t
  file-name-shadow-mode: t
  global-font-lock-mode: t
  font-lock-mode: t
  blink-cursor-mode: t
  minibuffer-regexp-mode: t
  line-number-mode: t
  indent-tabs-mode: t
  transient-mark-mode: t
  auto-composition-mode: t
  auto-encryption-mode: t
  auto-compression-mode: t

Load-path shadows:
None found.

Features:
(shadow sort mail-extr emacsbug message mailcap yank-media puny dired
dired-loaddefs rfc822 mml mml-sec password-cache epa derived epg rfc6068
epg-config gnus-util text-property-search mm-decode mm-bodies mm-encode
mail-parse rfc2231 mailabbrev gmm-utils mailheader sendmail rfc2047
rfc2045 ietf-drums mm-util mail-prsvr mail-utils time-date subr-x
cl-loaddefs cl-lib rmc iso-transl tooltip cconv eldoc paren electric
uniquify ediff-hook vc-hooks lisp-float-type elisp-mode mwheel
touch-screen dos-w32 ls-lisp disp-table term/w32-win w32-win w32-vars
term/common-win tool-bar dnd fontset image regexp-opt fringe
tabulated-list replace newcomment text-mode lisp-mode prog-mode register
page tab-bar menu-bar rfn-eshadow isearch easymenu timer select
scroll-bar mouse jit-lock font-lock syntax font-core term/tty-colors
frame minibuffer nadvice seq simple cl-generic indonesian philippine
cham georgian utf-8-lang misc-lang vietnamese tibetan thai tai-viet lao
korean japanese eucjp-ms cp51932 hebrew greek romanian slovak czech
european ethiopic indian cyrillic chinese composite emoji-zwj charscript
charprop case-table epa-hook jka-cmpr-hook help abbrev obarray oclosure
cl-preloaded button loaddefs theme-loaddefs faces cus-face macroexp
files window text-properties overlay sha1 md5 base64 format env
code-pages mule custom widget keymap hashtable-print-readable backquote
threads w32notify w32 lcms2 multi-tty move-toolbar make-network-process
native-compile emacs)

Memory information:
((conses 16 51324 17148) (symbols 48 5411 0) (strings 32 15047 1817)
 (string-bytes 1 418055) (vectors 16 8994)
 (vector-slots 8 128954 11248) (floats 8 24 21) (intervals 56 313 5)
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