On Linux, the Vanilla server's console does not handle the arrow keys correctly (other function keys do too). It will output ANSI code like ^[[A directly. Also in the output of "Unknown command" it seems that it is processed and the position of the pointer becomes weird.

It also happened when we try to remove a multi-byte character, such as an East Asian language, it will appear that it cannot be removed. Try to remove the character by pressing backspace will leave a blank space and the blank space is undeletable from console.

So it make us can't switch up/down commands in console.

Also the problem is not only with PuTTY and OpenSSH, but has been tested by multiple people and occurs on physical Linux servers as well.

We have tested vanilla servers from version 1.9.4 and they all have this problem.

Thank you for your interest in this issue.