Drew Adams <drew.adams@oracle.com> writes:

>> > IIUC, the meaning of "extract" in this sentence is to exclude the
>> > chars from the result.
>> 
>> No, I don't think it means that.  It means "take".
>
> Then I don't understand the "and should not be copied
> into other buffers" part.  I thought that text describes
> a situation where you want to return some parts, for
> copying to another buffer, and you want to exclude other
> parts from that copying.

For what it's worth, I read it like Drew does.  I also think giving
"characters" as an example doesn't make much sense, because I can't
really think of characters so "special to a buffer" that they "should
not be copied into other buffers".  Grepping the Emacs source, the only
example usage I found was in org-indent.el, which uses it to exclude
text properties, so I propose changing the docstring example
accordingly.