Gary,
As for your comment on them being in the minority, the same keyboards are supplied out here. Manufacturers don't change them for everywhere but the US...Yes I am aware that some 1/4" input jacks on keyboards have a switch for line or mic, and why do you think that is? it's because it switches between a mic pre-amp on or pre-amp by-passed for running line-level equipment, which is pretty much anything but a mic..you can use that line level for a mic but with quite poor results imo. All I am advising is that line level and Mic level audio pathways are different. As you would be aware some keyboards even have seperate mic in jacks/XLRs together with a stereo pair of jacks for the line gear..
Dennis