Is it your intention to create an inline translator without the need to prefix each line with the channel code? If so, for personal use you might consider using a third party viewer that implements the Restrained Love Viewer specification. Public chat can be redirected to a private channel.
"@redirchat:<channel_number>=<rem/add>"
"When active, this restriction redirects whatever the user says on the public channel ("/0") to the private channel provided in the option field. If several redirections are issued, the chat message will be redirected to each channel. It does not apply to emotes, and will not trigger any animation (typing start, typing stop, nodding) when talking." @ LSL Protocol / RestrainedLove API
However, this means trusting your Second Life password to someone who is not Linden Lab.