This really is a serious matter!!!
PUBLIC APPEAL TO THE MODS: Please confirm that you acknowledge this issue, and keep us informed ON THIS THREAD as to the steps you are taking to rectify the matter.
After all, if you (correctly) took steps to expose a certain poster for posting under multiple screennames, although all were his own, then you must surely stop people trying to post under other user’s screennames!
Thank you for bringing this to our attention. Good Shabbos.