A think a measure of common sense needs to be applied, the problem with common sense being that it blurs the boundaries of what is the exact legal behaviour required. As an analogy, suppose you are driving your car in traffic. The law not unreasonably requires you to look where you are going at all times, but this is not possible; you have to look away from the view ahead to check rearview & wing mirrors, or your speed on the instrument panel, warning lights, all sorts.
Applying this thinking to flying drones, then losing sight of a drone behind a tower for a second or so is similar to checking your speedo. Come to that, even when the drone is in full VLOS, you need to look away from it to check batterly levels, signal strength, &c on your screen.
The 5-0 will ignore all this, but if you do anything that damages a person or property, then their brief will bring a civil case against you and do his best to prove that you were flying negligently. Unless you have video of you clearly looking at the drone throughout the flight, he might be successful!
The 5-0 will respond to complaints, though, and this is where Karen comes in. Not much we can do about her, except maybe to gently point out that disturbing a pilot while he/she is flying an aircraft is itself illegal, and that so far as the CAA, who are the regulating body, are concerned, you are a pilot and your drone is an aircraft! Iām lucky, Iāve yet to encounter Karen, but my response to āIām calling the policeā would be āFine, please do, I want to make a complaint about youā.
If you fly sensibly within the spirit of the CAAās Drone Code even if it is impossible to do the letter, you will be ok! You will have flight records to prove that you were within that parameter.
Drones are capable of far more range than the Drone Code allows; mine claims to be able to reliably recieve RC signal from 5 miles away (just within out & back battery range) and transmit video from 12 miles away! I could do this by FPV legally with a spotter, but the rules are that the spotter has to be standing close to me and be able to communicate verbally, so he is legally no good 5 miles away on the phone!
I canāt really see my drone properly if itās more than about 150yds away, less if it is below the skyline (Iāve lost sight of it at 20ā at dusk against a dark background!). I can see it as a dot against the sky if itās 400ā above me, but if I glance away I have trouble relocating it. Paradoxically, I can see it at a greater distance at night with the aid of the Skytron Strobon light I can strap to it, probably up to half a mile in the right condtions of clear air and no ground light pollution. Does that count as VLOS? Taking it to ridiculous extremes, could I detect a reflected laser from a drone flying on Mars and claim that that is VLOS (Iād probably get into trouble for colliding with a NASA drone, but Iād be in the right because their drone is flying autonmously and not by VLOS)?
My advice would be to fly your drone where you can see it most of the time and donāt lose sleep over it going behind something for a second or so. If itās going to be out of sight for longer than that, probably best not to fly it there!