Possibly this is a bad explanation - I am tired - but I think what cimorene is suggesting is this:

At the bottom of my entries-crossposted-to-lj, there are some links and a comment count for the original post on Dreamwidth (the crosspost footer). Here's an example - This entry was originally... blah blah blah

For comparison, this is the original DW post. See how it lacks the crosspost footer?

So add a crosspost footer to the DW post which links to the LJ post and gives the comment count on the LJ post.

I don't know where we would get the comment count images, though. LJ and its clones don't generate those, as far as I know.