What's wrong with the operation is simple, yet important?
It's arguable either way. I'd accept it (so do report it and see what happens), but I can see a arguments against it, too.
Edit: Four months later, I am now a contributor and have added it. :)
Is the comma in the Swedish sentence required? Because it isn't in the English sentence.
No, it's entirely optional.
Operation here also in a military sense?
I suppose that would work, yes.
lätt vs enkel?
In the sense of not difficult, they're synonymous.
Could you add 'straightforward' for enkel, because this is how a doctor is more likely to describe it ? As I didn't risk using it I don't think there is any other way than in the discussion that I can suggest adding it.