Don't judge him.
Is widelcem in the instrumental case?
I think fork is in instrumental because it is preceded by 'we' which doesn't need to be translated separately.
I mean 'with'
so here, would "z widelecem" be nonsensical?
Yes, it would have the nonsensical meaning where the fork is eating as well.
Also, you have a typo, it's "widelec", but "widelcem". I remember that used to be a mistake in the Wiktionary declension table, but it's been fixed.
I put "czy je..." Instead of " czy on je..." but it wasn't accepted. Any reason why not?
I see this should have been accepted.
However, somehow I wouldn't omit "on" here - the sentence expresses surprise and putting both "Czy" and "on" sounds the most natural to me.
Wait, does the object always take the instrumental case when using jeść?
I'm not great with syntax, but I think the object (the direct object) is the soup... basically, the fork is "the instrument", so it takes Instrumental :)
Why is "Czy on je zupę ma widelcem" wrong?
czy on je zupe w widelcem?
I think that means 'Is he is eating soup in a fork'
Even though "w" can mean "in", I'm afraid that the entire phrase doesn't mean anything, as "w" and the instrumental case can't coexist.
why "je zupę widelcem" is wrong?
It's an accepted answer.