As I've observed, there are two "styles" to message-based conversations. Some people like to create long messages that are well sent as big, contiguous things. Others prefer a more casual style of SMS-like rapid-fire smaller messages. One good solution I've seen for this is the combination of messages from one person, interrupted only by the other person or a sufficient time gate.
I think it would be cool to see this grouping in the FN Message center, partially because each "Sent from" header takes up so much space, and then also because of the way individual messages each register in the Notification system. To be inundated with 10+ messages only to find out it was the next link in a conversational chain is a bit misleading, at least to whatever modern notion of Messages I've gained thanks to the likes of Twitter, Facebook, etc.
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