[design] unintended attachment

I have no idea why all my resent posts to design-l have an
attachment of a horizontal line image at the end of each
post. I've tried to find the problem at my end, alas to no
avail. All I know is that it happens only with my design-l
posts. Anyone here know what may be causing this?

I'm curious to see if this post, which is a new email as
opposed to a response to another post, will also have the
unintended attachment.