I don't find it ambiguous at all.
He ignored the person, not the fact that the incident took place.
Suppose Albert is unhappy about some incident that Joseph was in involved in. Then Albert walked by Joseph on the street, but didn't talk to him.
"Albert ignored Joseph over the incident."
Could this be ambiguous? I want it to mean that the ignoring was in retaliation for the incident. But it could be read to mean that Albert ignored Joseph on the topic/issue of the incident.
I don't find it ambiguous at all.
He ignored the person, not the fact that the incident took place.
I'm not a teacher, but I write for a living. Please don't ask me about 2nd conditionals, but I'm a safe bet for what reads well in (American) English.