[lmm]

> Messenger apps don't claim that this history should be global and consistent.

The fact that we're talking about multiple people looking at the same chat - the fact that we do conceptualise it as "the same chat" and "the history" - implies that we think of it as a single thing. And I think messenger apps generally nudge us that way - e.g. setting the name of the chat usually sets it for everyone.

> It is the order people (and their records, if they have some) would have had in mind in the old time.

I don't think it is. If I pull my correspondence with person X out of my drawer or file, the only dates I have to order them by are the dates written on the letters - which are the letters they and I (if I keep carbons of the ones I send) wrote them on, not the dates I received them. If they sent me a postcard while on holiday and then a letter after returning that arrived sooner, I'll read them in one order on receipt and in a different order when looking back. Likewise if I have a memo of a phone call with them, that may be from before I received a letter that is nevertheless dated earlier.

[deredede]

> I think messenger apps generally nudge us that way - e.g. setting the name of the chat usually sets it for everyone.

That's a good point - maybe it's actually email that warped my mind.

> I'll read them in one order on receipt and in a different order when looking back

Also a good point, I was thinking more about business communication where the date the letter is received matters. Thinking back on it, I think the main difference is that the messenger apps might happily reorder message before (or while) I read them. And if only one order is to be available, the one of the most use to me for an instant messaging app is the one I received the messages in, but I get how for other use cases it would be different.