As we still get incidents where staff think they are communicating in an internal/private message but accidently send it to the customer. It has been made more clear in the last few updates with the yellow color etc.

But our feature request would be to completely separate this from the normal "Send message" function. Something like its own separate tab up the top between "All Activity" and "Customer History". Or add something like "Internal comments" to the ticket details location on the left.

Giving it a separate position so that it can't be mistaken.