I would be interested in reading opinions in regard to this video - link at the bottom of this post. It's a range test by a well-known YouTuber and drone flyers influencer. He maintains that the flights are legal because he has a spotter positioned a mile or two downrange and in contact via two-way radio.
He further claims that a contact who works for the FAA, as well as the owner/operator of REMOTEPILOT101.com, agree that using a visual observer who is not within unaided sight or earshot of the pilot in command (PIC) of the drone makes it legal for the PIC to fly BVLOS.
The FAA regulation covering VLOS below seems to back this up. The enlarged bold text below and in particular the word "or", at least the way I read it, means that, so long as the visual observer can see the drone, the requirements have been satisfied. The wording is annoyingly not 100% clear.
107.31 - Visual line of sight aircraft operation.
(a) With vision that is unaided by any device other than corrective lenses, the remote pilot in command, the visual observer (if one is used), and the person manipulating the flight control of the small unmanned aircraft system must be able to see the unmanned aircraft throughout the entire flight in order to:
(1) Know the unmanned aircraft's location;
(2) Determine the unmanned aircraft's attitude, altitude, and direction of flight;
(3) Observe the airspace for other air traffic or hazards; and
(4) Determine that the unmanned aircraft does not endanger the life or property of another.
(b) Throughout the entire flight of the small unmanned aircraft, the ability described in paragraph (a) of this section must be exercised by either:
(1) The remote pilot in command and the person manipulating the flight controls of the small unmanned aircraft system; or
(2) A visual observer.