[exim] The Bcc Issue (revisited)

I recently had someone complain that he sent (from micros$ft machine) an
important BCC'd message where some people could see the BCC recipients.
I was on that recipient list, and indeed using Thunderbird *I* saw all
the names. He was slightly embarrassed and considers it the ISP's fault.

I've read up within this group's postings, and see that much discussion
went on about whose's responsibility it is to NOT post the BCC's;

Aside from all the previous debate, is there any "harm" in having exim
remove BCC lines while in the delivery transport?

Jim