Looks like it's replacing "localhost" with the IP address. You can control what the prompt looks like with a configuration which you write into .bash_profile. Giving your computer a name other than "localhost" might also make a difference, but I haven't checked that.
On a computer here there's
in the .bash_profile which produces a prompt with the user (\u), hostname (\h), and the basename of the current directory (\W). See man bash for the details.
You can change the name of the computer using the hostnamectl command, that'll control the \h part.