>> +(defcustom completion-allow-text-properties nil
>> +  "Non-nil means `choose-completion' should not discard text properties.
>> +This also affects `completing-read' and any of the functions that do
>> +minibuffer input with completion."
>
> This new user option should be announced in NEWS.
>
> I also wonder whether it should be a user option

So here it's a variable, that will later help to select Imenu
completion candidates with same names from different groups.