I can "dismiss" but not unshare. And I can't even select to unshare comments on other blogs where I am only an author (as opposed to moderator status which I have here).
ETA: For Kinja Help Tag / Documentation
It seems very odd, as a test, I "dismissed" a comment through this option, which was shared from within Oppo, and it dismissed the comment in the original thread as well as removing the share.
So what will happen if I "dismiss" the share from the front page? And why is the dismiss option tied to unsharing a comment?
ETA2: It's there for some shared comments, but not others.
ETA3: It seems that only moderators can unshare some comments (in my testing), and others, it seems no one (except maybe other than the sharer?) can unshare . Such as the one pictured at the top of the page, I cannot unshare it from oppo).