I thought of this as well. Reposted cards are marked as reposted, but to the uninitiated reader there's nothing to indicate how much of the card's contents are original vs new thoughts from the owner of the rest of the stream. Actually, of course, 100% of the reposted card's text is original, but the nature of that text can often make it ambiguous. For example, if the reposted card includes a quote and a response, how is the reader supposed to easily divine that both the quote and response are included in the repost?
Anything that reduce the likelihood of other people's words being mistaken for your own would be welcome.
Ideally, one or more of the following: left-shifted margins; reposted card's author's avatar; slightly darker background.
(In my thinking, shifting the margins of reposted cards to the right might make it appear that the repostee was "replying" in some sense to the reposter's thoughts, which is often not the case.)