That's something that Telegram always seems to get right, I've never seen messages out of order in different clients, and if I do something like upload a video then immediately send more text messages before it's done, it will shove the video in between the messages where it should be when the upload is done.
I know it's a much harder problem without a central server managing things. But consistency is very important for messages, out of order they could have a very different meaning and be very confusing.
> I know it's a much harder problem without a central server managing things.
In got example it is easy if the structures relating to the video and text contain some what to identify the source node, or just that they belong to the same lineage (you could have a per-thread-per-source-node value, produced from a salted hash of the real information, if source host Id is considered sensitive) and a timestamp taken at that node.
(Caveat: I know little of the specific protocols that are relevant here, so don't know if they do contain any such datum)
Where message ordering gets difficult to the point of impracticality (if not impossibility) is where you are ordering messages from many different sources that may not have fully synchronised clocks. You can make it easier with "in reply to" and "sent after" priorities (in each case, the value being a message identifier) so any given message can be sorted by its context, but the order of sibling messages may still not have a single possible ordering. And you have to decide, if using a "sent after" value, if you have the last message received at the time of sending, the last message received before this message was stated, the latest opened messages, etc, all of which could give different results.
To a certain extent you have to get to a point where ordering is good enough and you give up on it being exact & unambiguously consistent, or you'll spend so much time working out the ordering and have no time to send you own messages :)
I know it's a much harder problem without a central server managing things. But consistency is very important for messages, out of order they could have a very different meaning and be very confusing.