It does seem true that there is either some level of subjective judgment in determining the level of severity, or that the factors involved may be considered by the IAEA (perhaps due to pressure from the nuclear power industry) to be too morbid to have a public debate about. This quote from an article referenced in the Wiki entry worries me: "Each country has an INES National Officer who liaises with an IAEA reporting centre to disseminate information in consistent language." http://www.world-nuclear-news.org/RS_Event_scale_revised_for...

Who knows how much independence these national INES representatives have from their countries' nuclear industry, and how strongly public interest is considered by these people.

There is also some mention in the same article that the INES scale is intended to be logarithmic, with each successive level representing ten-fold increase in severity, but it is not made clear how the various factors are weighted.