While I’ve never really tested the (non-)effect of cable risers I wouldn’t rule out they’re having an effect, whilst quickly saying that if expensive cable risers of some more or less exotic material are promoted as having the biggest, most positive effect I’ll laugh it off as a load of b*llocks, safe for acknowledging mere coincidence. Really, why in the hell is it close to always the most expensive materials (and configurations) that are the most highly touted in the hifi business - with the claim that they’re sonically superior, that is? Go to a jeweller and find out..
(De-)coupling of components has an affect for sure, but it’s assessing what approach has the most desired impact. I have a DAC/preamp on loan these days as a possible item to replace my existing DAC/preamp, and tried it out initially without my Ringmat Domes (made of compressed cork) underneath it. I was later shocked to find out that the biggest difference in sound between the two DAC’s was due to using or not using the Ringmat Domes. Not highly relevant to this thread, perhaps, but still a humbling experience that could be related.