If a low power licensed station is interfering with someone's reception, this
is that someone's tough luck. Not so, with unlicensed operations.
That's what the owners of licensed stations will tell complaining neighbors. The station may be required to prove that it is operating within it's licensed power and is not emitting signal that violate technical standards.
A 100 watt LPFM will overload receivers for one half mile. If a part 15er is
overloading radios at this distance, it is not part 15 and is called harmful
interference by the FCC.
Show me your calculations on that one. I have been grinding some calculations where you have a choice to put out 100 watts on a 100 foot tower at one location or move your tower a mile and be on a hill 200 feet up with a short tower (25 feet?) and maybe 16 watts of power or a mile in another direction and be on a 400 foot hill and with a 25 foot tower be limited to 6 watts.
Sounds like a great idea to have a tiny little transmitter at very low purchase price. The trouble is, it may not penetrate significant buildings at half a mile, and is not likely to overload receivers.
The other calculation I have been doing is determining how low your antenna can be and not put out enough radiation to be unsafe for humans to be at ground level right under the antenna. Assume for a minute you take a small bungalow and convert it into a station facility and mount the antenna maybe only 10 feet above the roof. How much power do you have in the area where the volunteers will be working and is it legal.
I'm not sure what it takes in signal to "swamp" a receiver but I suspect a 100 watt LPFM with an antenna at 100 feet might cause some difficulty out to about SIXTY FEET from the antenna location at the most.