Dear all,
"delete" button on vi that kicked off from terminal emulator doesn't work. When I'm in insert mode, then I press "delete", it goes back to command mode.

How can I fix this?

Regards,
ethereal1m

I just tested, and Konsole and vi behave correctly ( ie. delete performs the correct action, not returning to command mode )

I'm using KDE 4.3. Is this related to the version? Or is there any environment variable that I need to set?

Issues such as this are usually not related to Konsole version, but to Keyboard layout or environment variables.

how to troubleshoot this? because with tty1, i don't have problem with vi

Unfortunately I don't know much, but you could try checking the setting in Konsole > Settings > Edit Current Profile > Input.