🚀 go-pugleaf

      So, what exactly does this ground do?




Provides a safety ground connection - it also protects the system rather more from lightning strikes. You would be better off contacting the cable company and asking them to provide the isolator, and then grounding the box separately from the cable splitter - that way, you haven't potentially invalidated your contract with them, which probably has something about this in the small print.

      I'm hoping the cable company might provide me with the isolator...and
      hoping I don't lose picture quality because of it.




You won't lose any quality at all - this is an RF signal that's being isolated, not a baseband one.

      Am I gonna die if I leave it unconnected?




Yes, certainly you will die (after paying some taxes) - but I don't suppose that there will be any sort of relationship, however tenuous, between this and the disconnection....