Does raising speaker cables off the floor really make a big difference?

audiozenology, this is a good example of why you should never trust anyone's hearing. I have also seen instances in which these "AB" comparisons were rigged by someone switching EQ curves or phasing.
If you can not think of a reasonable reason why something should work it usually does not. Cable elevators are a good example of this. There is no reason and they don't work, not even a little except in the minds of the easily influenced.

I’ve just read through this thread and it would appear there are people in both camps.

I am not surprised some people hear a difference and others do not, because we are all using different cables 

The one omission throughout the thread was
- NO ONE in either camp has identified the cables they are using.

What difference does it make? you ask...
- due to cable geometry, some cables carry so much internal noise that hearing the difference cable risers make is next to impossible

- others geometries reduce the amount of noise, so using cable risers with those would demonstrate the improvements.

- Also the insulation used in cables has an impact on the amount of noise generated internally.

Many years ago I tried cable risers with one of my older speaker cables and they made no difference, but with the cables I now have, lifting them off of the floor did improve the sound.

So - how much benefit is heard depends on the "geometry" of the cables and the insulation used.

- If you use simple geometries i.e. two wires side by side such as Van den Hul CS-122 or the NAIM speaker cables the improvement would be difficult to detect

- with geometries like the Planus III cables used by the OP, I believe they would benefit from the use of cable risers.
---- those big flat cables sitting on carpet or wood would have more internal noise than if suspended on cable risers
---- As one of the other posters mentions it’s all about dielectric influences of the floor on the cable/signal
---- Man Made Fibre Carpet is especially bad - wool would be better

For myself - I use a HELIX geometry in all my cables
- the signal wire is suspended in the center of a Helix Neutral coil by spaced wood beads, so a high percentage of the dielectric between the signal and the neutral is actually air
- also the coil acts like a faraday cage, so external RFI/EMI in the signal wire is very low
- the resulting signal that reaches the speaker is almost noise free
- hearing the improvement was quite discernible

I use DIY wood risers with a ceramic base that lift the cable up about 3/4". I did try lifting the cables higher, but there was no improvement.

Regards - steve

As to soundstages collapsing due to cables not being treated as if they were unicorns: I have friends and acquaintances who are audio reviewers. I regularly hear whatever gear they have in, from expensive amps, to all sorts of speakers, all of them hooked up to super high end cabling.

Every time I come home from listening at their place I play the same tracks on my own system and...somehow....with my 35 foot long generic cables running under floors and over a rug....I experience glorious soundstaging and imaging (and clarity) of at least the equal if not more to what I’ve heard there. I guess I’m just lucky. (It’s ok, I’ll do this for you: "that’s because you have ears of cloth, not carefully trained golden ears like the rest of us")

Speaker set up/room acoustics/listener position will in all likelihood influence imaging/soundstaging far more than raising the average cable off the floor.

Absolutely no difference in my system.