It already is, Beside the chat names should be something like [N1] or [N2] This means its cross node.
between nodes is implemented and between servers has been discused but was decided that it would be to confusing.
I think it would be a cool thing if u can toggle it like /chat global (every server) /chat server (only on the server you are on) /chat mod pack (between nodes)
Between different packs it would get highly confusing. Some one on Infinity talking about Draconic whatever, and some one on Regrowth wondering how to get it. Different mods and even different recipes between different modpacks would mess up things.
The problem wouldnt be there if the default setting was "server". With an option to change it to "global" Only if you wanted to. Would prevent confusion as you would know you are in global. And each person would have ["servername"] By their username.
I assume this is about private messages. If so it has been on our todo list for a year or longer. Makeo worked on it for some time but gave up, since no one has picked it up.
as it was already started and is on the list I'll mark it as accepted but when we will resume on it, I don't know.