I was chatting with Matt earlier about this and related issues, and we tossed around the idea of a processing hints marker, such that a sender could indicate that there was no point archiving, or that carbons were useless (because the message used OTR, perhaps), or that the message was actually useful for offline storage despite not having a body, or that the stanza wasn't urgent (and so needn't be flushed to the client immediately, cf google:queue).
The notion that these hints would be potentially ignored by naïve entities would need careful consideration - in this particular use-case, we'd need a way to re-request a chat state, for example. Does the community think this is worth exploring, with a view to addressing a number of these issues?
