[akjj]

This is right, but the canonical/non-canonical distinction is all or nothing. Bash echos most characters, but it needs to treat a handful, like tab, up, and down, specially so it (or readline probably) puts the terminal in non-buffered mode and ends up echoing the normal characters. I read the GP as suggesting that there should be a way for bash to indicate which characters were "normal" and should be buffered and echoed and which it wants to see immediately. It's an interesting idea, but of course such a mechanism would require coordination between the kernel's terminal interface, bash/readline, and ssh in order to get a marginal improvement in network efficiency.