Current behaviour: Blindness's (SPWI106.SPL) spell description is inaccurate. It currently states: "If a victim is blinded he receives -4 to hit on his attack rolls, and has a 4 point armor penalty." In reality, blindness actually afflicts the target with a hefty -10 THAC0 penalty, and there is no AC penalty at all.
Suggested behaviour: The spell description should be updated to reflect the actual penalties of blindness. Or, Opcode #74 (Blindness) should be modified to inflict -4 penalties to THAC0 and AC, which is a more balanced solution, in my opinion.