RIAA vs Columbia vs Decca

Reissues are most certainly RIAA. I can't imagine any modern recoding engineer using anything else.

Lewm, I think Chakster was referring to "Absolute Polarity". That will open up a can of worms. Some claim that it makes a difference, others claim that they can't hear any difference. I believe JGH was in the latter camp. I definitely reside in the former. That said, older LPs are all over the map when it comes to polarity. Even new releases do not always hew to the standard. Diana Krall's album "Quiet Nights" comes to mind. The new Eva Cassidy releases which are compilations from various sources has some songs recorded in positive polarity and some in inverted.

If you think about it, air is not a linear medium. One glance at the adiabatic pressure/volume curves of an ideal gas will convince one of that. This results in the asymmetric distortion of the sound wave. Common sense would suggest that inverting an asymmetric wave will change the sound. I guess the take away here is if one's system - ear/brain is sensitive to absolute polarity then it is very handy to have polarity invert on remote control.

Also, it wouldn't surprise me if in some cases where listeners perceive differences between the two settings of a preamp's polarity inversion switch what they are actually hearing is changes in the sound of the preamp itself, that result from the differences in the preamp's internal circuit configuration between the two settings.

Not the case with my set-up. Polarity inversion just reverses the phono preamp's line out transformer's secondary winding.