currently, /etc/profile checks for the existence of a $HOME directory and if it does not exist, creates it and copies /etc/inputrc.default to "$HOME"/.inputrc.
However, sometimes I install MSYS and have already set the $HOME variable to another directory. Thus the .inputrc file is not copied over.
I suggest to make the copying of .inputrc independent of the presence of the HOME directory, but actually check for the presence of this very file instead. the attached patch against /etc/profile does this.