I found in the DI specification a ReferenceType beeing symmetric and hierarchical (ConnectsTo).
That seems fundamentally wrong to me, as a hierarchical Reference always implies an "up" and "down" (parent / child) inside a hierarchy (at least to me). However, I have not found any statement in the spec, stating that this is not allowed.

Consequences if we clarify it: DI spec becomes invalid - we would need to add a mantis issue there.
Consequences if we leave it open: Tree views using hierarchical references will automatically run into a loop since with those symmetric, hierachical references as the child points to the parent with the same reference (not the inverse one).