Yeah, it is a problem. RSS helps with reading somewhat, but for commenting and other things, the protocols simply haven't been developed yet and the tech isn't there.

I don't think it'll be much of a difference. The feature is only available to paid users, which inherently limits it, and also, it depends on what the definition of 'bail' is. You'll still need to have some kind of LJ account to be able to comment on the posts and interact socially w/ the people on LJ, so is that considered 'bailing'? I'm also not sure what it would tell us about the value of interoperability: I'd be far more curious to what extent crossposting to WP or Tumblr gained adoption.