Technically, you can't cast all those lethal U spells on other people. . .like boiling their blood or such. . .but you can cast a U spell on a willing target, so you technically could U spell willing yourself.
A lot of those really nasty cursed scrolls are like:
RR or turn all bones to jelly
or
RR or blood boils.
or
RR or heart turned to stone
And it struck me, that in some ways those are a lot like self inflicted U spell fatalities. . .in a way of looking at it, the RR is how well the scroll did in tricking you into casting a fatal U style spell on yourself, but once cast, you're just doomed to a self inflicted "Willing target" U style spell death. . .