ToME WikiWastrel: In Vanilla, an attack that lowered the character's level would reduce max hitpoints, spell points, abilities and spell access.
In ToME, prior to 2.3.0, such an attack would lower all of the above except spell access.
In ToME v2.3.1, such an attack only lowers max hitpoints and spell points.
Ideally, skills would be lowered too somehow, so that access to some spells could be lost, as well as a lowering of abilities (which are now skill dependant). Actually losing and regaining skill points would probably be bad and open to all sorts of abuses. But the Max skill and current skill could be stored in a manner similar to stats and experience.
NeilStevens: Not quite true. Experience drains have no more or less effect in 2.3 than they do in 2.2. They do have less effect in the whole ToME 2 series than in Angband, though, because so much is dependent on skill level instead of character level.
In any case, you're mean, heh.
Wastrel: I'm not mean, I just want to give those poor undead a sporting chance 
In 2.2, didn't mearly gaining a level boost abilities (such as fighting, saving throw, etc.)? So wouldn't losing a level lower them as well? Or did they just stay at their last max like skills?
NeilStevens: Character level didn't make a difference. What changed in 2.3 were racial bonuses, and the effect of class on the bonuses from skill.