It would be great if each topic had URLs of both the local and online version of the article somewhere on the page. This would make it very easy for someone who is browsing the local BOL to copy the URL for the same topic online.
Failing that, how about implementing a bookmarklet feature, like the one Steve Kass recently created, to make this easier for everyone (not just those who found his article and are willing to do it):
Steve's solution is great, but it is not as automated as it could be. If he can come up with that in his spare time, surely the product could include some similar functionality in the next version.