There is indeed a wealth of crap on that website, but this isn't it.

Digital signals are in fact no different to any other signals, and
they are most assuredly analogue.

For a very simple network pulses will be put direct onto the wire, eg at
any time it will be either 0v or 5v, and nowhere imbetween, this will
create the square wave that is sometimes called a digtal signal.

The distinction is much less clear for a modulated signal, which is just
about every signal these days, but I don't think its correct to simply say
Digital == Analogue.

However...

It is just the information they
contain that isn't, but as far as the signals themselves are
concerned, all the normal analogue factors of frequency response,
phase response and distortion have their part to play.

....this is complely true. That's why repeaters exist to transmit digital
signals over long distances. However on plain old cat5 a high speed signal
can travel (IIRC) 200meters without special equipment.

I've said before, digtal HiFi interconnects are possibly the least
demanding application imaginable. People who buy high-end just don't like
to think *anything* their equipment does is actually easy!

--
Jim H