When I first saw your post, I got curious and checked any unlocked entries on your LJ, so I'm glad I didn't jump into the "I has yaoi! Let me show you it!", which tends to be a reflex reaction of mine.

But yes, considering how much Buggy sneers and laughs whenever someone attacks him with an edged weapon, I can see him reveling in the fact that he can't be cut anymore as soon as he figures out what his Devil's Fruit power does. And considering that Shanks is a good guy, and he wouldn't want to hurt someone he considers a friend -- at least not in a permanent, debilitating way -- I figure that he'd have a problem with intentionally shoving a knife into Buggy, despite all evidence that Buggy can't be hurt that way anymore.