+1. The "sans interactions" angle makes sense to me, since there's no interactions system here to attach an EPHEMERAL flag to, so a plain flag plus a target user id feels like a more natural fit.
Could be missing something on the internals though.
Besides the privacy angle, these are really useful for bot feedback that shouldn't sit in the channel forever: "that command didn't work", "your upload failed", "only you can see this" confirmations, that kind of one-off reply to a single person.
From a quick look, the schema side seems small (the server only allows a fixed set of message flags today), but the part I'm less sure about is the gateway having to deliver MESSAGE_CREATE only to the target user's sessions instead of the whole channel.
No idea if that's the right way to do it, just what stood out to me.
Either way, would love to see this land.
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Comment by @noxied