So I ran into this problem on the mars server. If you log in and try to hit "backspace" or "delete", the console won't actually delete characters, it will instead print "^?".

A temporary fix for this is to type into the console "stty erase" and then press the backspace key. (It will look something like "stty erase ^?", this is fine). After this just hit enter and you should be able to erase.

Basically you are registering the backspace key as the erase function for the console.

It's a temporary solution though, I think you have to do this every time you log into the mars server. Not sure how to permanently bind the backspace key to erase.

You can try holding Shift and then Backspace.