>> +(defcustom read-char-by-name-group-sort nil
>> +  "How to sort groups of characters for `read-char-by-name' completion.
>> +When t, sort sections of Unicode blocks alphabetically."
>
> This doesn't say what happens if the value is not t.  And since the
> first sentence says "How to sort...", the idea that the result is
> unsorted group names doesn't come to mind naturally.

Now read-char-by-name-group-sort is removed, since this can be
customized by completions-group-sort-function.