leaders acts like glue so is dropped at a line break
\documentclass{scrartcl}\usepackage{polyglossia}\disablehyphenation\newcommand{\sep}{\unskip\space\xleaders\hbox{*}\hskip\fontcharwd\font`\*\relax\space}\begin{document}\parbox{9cm}{%Arabel \sep Dusty \sep Octavia \sep Dinny \sep Demetris \sep Thomasa \sepCherie \sep Deeann \sep Page \sep Jesse \sep Kitti \sep Ruthie \sep Cory \sep Kathleen \sep Kaylyn \sep Chelsie \sep Floe \sep Verna \sep Torey \sep Cissy \sep Nora \sep Krissie \sep Hesther \sep Virgie \sep Liliane \sep Abagael \sep Joyann \sep Siobhan \sep Pierette%\parfillskip=0pt\par}\end{document}