Happens rarely and isn't justified most of the time. Only people who ever deserved ban for that are those two CamelRiders and not because they allowed dueling, they enforced dueling on EU4 constantly for a very long time before they finally got banned for it.
I agree with Umbra, quite silly ban request. I'm not Friedturtle's fan either but what he did isn't against the rules. And I do understand how Herezy felt, I hate when people stand aside watching how two guys fight on big server. I'm against dueling on EU1, if there's more than 10 players left but what he did is not against the rules (you should ask someone who died to QML him, beer
).