Do not export PS1 and PROMPT_COMMAND

[h3xx]

PS1 and PROMPT_COMMAND are never used outside of bash. There's never a
reason to export them into the environment variable arena.

[blieque]

What if someone launches a new instance of their shell from within the shell? I know it's an add thing to do, but someone may have a reason to; I know I've done it before. Without export the variables would not be passed into the new shell.

[h3xx]

What if someone launches a new instance of their shell from within the shell?

When you type bash into a terminal running bash, it re-executes your .bashrc. If you put the PS1 setting in your .bashrc like the file says, it'll still work.

Source: I just tried it, after making sure PS1 wasn't in my environment.

[blieque]

Very good point; I'll merge your changes into my fork.