Sure, do something between an article a wiki and a forum.
Insert your cursor in their message, press enter and respond to every part worth responding to - inline. (you may want to sign your entry)
Remove all parts of the previous message(s) that do not directly build towards the current conversation.
It should look so organized that the new participant immediately adopts the format. If they fail, do it for them. (preserve the sane part of their signature)
Doing it like this really feels like you are talking with serious people who would never waste your time. That said, you can now ask how their weekend was. That part of the conversation is simply removed later on.
Insert your cursor in their message, press enter and respond to every part worth responding to - inline. (you may want to sign your entry)
Remove all parts of the previous message(s) that do not directly build towards the current conversation.
It should look so organized that the new participant immediately adopts the format. If they fail, do it for them. (preserve the sane part of their signature)
Doing it like this really feels like you are talking with serious people who would never waste your time. That said, you can now ask how their weekend was. That part of the conversation is simply removed later on.