I'm not sure if this was already planned to be implemented. Currently, if you start a private conversation with someone and switch SMPs, it moves you back into community chat. It would be nice if it keeps you in the same conversation because it's easy to accidentally send something to the wrong channel and it can be annoying if you're jumping SMPs a lot.
It's better to accidentally send something in private than to accidentally send something in public, I'd say!
This is definitely planned. IRL has gotten really busy the past week - but chat improvements such as this are at the top of my list.