If you cross-post, that sub gets it’s own up/downvote count. You would have to open the link and go to the original post to see and affect them, so it already discourages brigading.

NP is when I link you directly to somewhere, e.g https://np.reddit.com/r/comics/comments/1j4scuu/barbie_doll/ won’t have voting even if you are logged in, not on the post or the comments.