See org.hibernate.search.indexes.interceptor.EntityIndexingInterceptor.

Note: we'll have to provide a way to ignore interceptors, most notably because calls to org.hibernate.search.FullTextSession.index(T) are not supposed to be intercepted.

The javadoc for EntityIndexingInterceptor mentions "soft deletes" as a use case for interceptors, we'll have to make sure that at least that one is covered.