I don't think this is entirely accurate, as sites like Facebook and YouTube have had large mod teams on their payroll for years and still have safe harbor protections for user created content.
What I could see happening in this case, is safe harbor protections no longer applying to accounts with mod privileges, possibly even those who aren't being paid. If Reddit started paying mods, it could be reasonably argued that mod status constitutes an endorsement / publication by Reddit inc for anything a mod account posts. It would also give anyone working as a volunteer mod cause to sue for unpaid wages.