Shoutbox

seems a bit overcomplicated and quite possibly impossible to implement

most people are competent enough as conversation to be able to distinguish between replies to certain questions

or if necessary just speak about the one thing, and then remember the second for later if you have trouble talking about more than one thing at once

or if you want to have the two conversations, use the Plus! feature to change text colour or style as you type

"[ b]" "[ /b]" tags will bold the text or you could use italics, different colours, etc