ynyaaa@gmail.com writes:

> Evaluating the form below, five U+4E00s are inserted with same glyphs.
> C-u C-x = on each character shows the same information.
>
>>              display: by this font (glyph code)
>>    uniscribe:-outline-Noto Sans CJK JP
>> Regular-normal-normal-normal-sans-17-*-*-*-p-*-iso8859-1 (#x2667)
>
> (let ((prefix "-outline-Noto Serif CJK JP-normal-normal-normal-serif-*-*-*-*-p-*-"))
>   (set-frame-font "Noto Mono")
>   (set-fontset-font "fontset-default" '(#x4E00 . #x9FFF)
>                     "Noto Sans CJK JP Regular")
>   (insert "\x4E00"
>           (propertize "\x4E00" 'face '(:family "Noto Serif CJK JP"))
>           (propertize "\x4E00" 'face '(:font "Noto Serif CJK JP"))
>           (propertize "\x4E00" 'face (list :font (concat prefix "iso10646-1")))
>           (propertize "\x4E00" 'face (list :font (concat prefix "jisx0208-sjis")))
>           ))

(I'm going through old bug reports that unfortunately weren't resolved
at the time.)

Trying this in Emacs 29, I get a different font on the second char: