I think there's essentially no good blanket answer to the issue of comment ownership. Both commenter and entry poster have some legitimate claim to the content in the vast majority of cases. In practice, it's an incredibly small minority of comments that could be reproduced somewhere else that would be of any relevance whatsoever, and of that minority, another incredibly small minority would ever actually be reproduced by the journal owner.

Of that miniscule subset of relevant content that actually has/will be reproduced, I think you pretty much end up with gossip or some other form of high drama as the only real content type. Should service providers care if someone's gossip gets reproduced somewhere else? Probably not.

In a nutshell, I think the entire issue is a big grey area, and there has been a huge blowup over a lot of theoretical grievances that are incredibly unlikely to ever occur. I'd much rather see that kind of reaction in the face of something that truly warrants it, because if every little change gets this sort of reaction, each event is going to have a diminishing effect on the people trying to decide if they really need to revert or significantly change whatever caused the reaction.