Ideally, I would always like to be able to up-vote a submission while reading it. Since most submissions are of off-site content, I don't always have the capability to do this. Instead, I have to come back to HN after reading, search the list to find the submission again, and then click the up-arrow.
It would be ideal if a link to off-site content opened up a viewport page, with the content in one iframe and various HN-related controls in another iframe. Users could opt-in (or opt-out) of this behavior.