The motivating example is a quote from Jane Austen:

> 
> Be not alarmed, Madam, on receiving this letter.
> 
> 
> 

Note that she starts with "Be not alarmed".

If this were, instead:

> 
> Don't be alarmed, Madam, on receiving this letter.
> 
> 
> 

would that have the same meaning? What is the difference between "Don't be alarmed" and "Be not alarmed"?