>> I can't believe this, in particular given that the default value of 
>> enable-recursive-minibuffers is nil.
>
> You again are thinking only about uses of mini-window for editing in the 
> minibuffer.  But that is not the only use of the mini-window.
>

I'm not sure I understand what you mean, but it seems to me that these 
other uses of the mini-window are not at all affected by the proposed 
patch, given that `start-display-at-beginning-of-minibuffer' is reset 
immediately when read_minibuf() / read-from-minibuffer has ended.

>
> And even in its use for the minibuffer, many users enable recursive 
> minibuffers.  I would not be surprised if some specialized modes and 
> packages enabled it for their operations.
>

If this case is important, the attached corrected patch also disables 
setting `start-display-at-beginning-of-minibuffer' in recursive 
minibuffers, that is, it limits the effect of that variable to 
non-recursive minibuffers.

I'll wait until you and Stefan agree on the way to solve that problem in a 
better way to start working on this.  In his last mail he is apparently 
not sure anymore that using text properties to do this, as he suggested 
yesterday, is the best solution.