Speaking of unquiet spirits from unsuccessful wars--in this case my own from my neverending battle against the shakai kakusa hysteria--reader Etienne writes in comments:
The NBER has an interesting paper on top income inequality in Japan over the long term (1885-2002). It shows that the bubble had a relatively low impact on wage income concentration and that the equalizing effect of the institutions created in the immediate post-war period was not really reversed. As for the impact of the Koizumi reforms on income inequality, the jury is still out.
Now if anyone can teach me how to get my comments up in something other than gigantic white script, I would be much obliged.