>> My admittedly not well-calibrated lisp tasteʼoʼmeter doesnʼt find
>>
>> (format-prompt "Prompt" nil :default "all")
>>
>> all that appealing either
>
> <Shrug> Then I hope someone will come up with a better idea.
>
> My point is that using format-prompt obfuscates the code to some degree, 
> and we should try to find a way of avoiding that, while keeping its 
> advantages.
>

FWIW, I'm not sure using minibuffer-default-prompt-format is optimal in 
this specific case.  Before the change the prompt said:

Character (Unicode name or hex, default all):

Now it says:

Unicode name, single char, or hex (default all):

or, with minibuffer-default-prompt-format set to "":

Unicode name, single char, or hex:

IMO, the original prompt was much clearer, and I don't think those who 
customized minibuffer-default-prompt-format would have protested that this 
specific prompt does not obey their customization: "Unicode name or hex, 
default all" is an explanation about the kind of input that is expected, 
like the one we have for C-x 8 RET, which says:

Insert character (Unicode name or hex):