Howdy Andy.....Reread what Ralph described to you carefully and, when
you
think about it, you'll see that he's described exactly the same
reasoning
amateur repeaters use PL tones, with the same benefits and consequences
if their use is misunderstood (a user who, using the correct PL tones,
and is accessing a repeater may be interferred with by another station
transmitting on the same frequency but not using PL tones or who may be
using a different PL tone...of course the difference in signal strengths
received by the repeater will determine the degree of interference).

Maybe some amateur repeaters are transmitting a PL tone....if so I
didn't realize that, and persons in the coverage area could be open to
interference if for some reason they attempted to share the frequency
using a different tone or no tone (and vice versa). The best bet, as
we all (should) know, is to listen first, ensure the frequency is clear,
then transmit.