It is clear that Ingress listens to its user and you can now onion field again. This change, which ocurred 24 hours ago, has been reverted.
The ingress gameplay changes just keep coming.
At some point in the last 4 hours a change was made to the way linking to portals within a field works.
While attempting to link to a portal inside a field and layer or “onion” the field, in order to double the MU’s earned, the key refused to populate.
A quick search only led to a post by agent Gilles WEBER where-in Ingress states “If a Portal is inside an existing Field, it is no longer possible to establish a Link to that Portal. You should still be able to create Fields over existing Fields, but not Fields nested inside existing ones.”
This is a big change for long-term agents who are accustomed to layering fields as part of general play. This change will also have an effect on Regional Scoring.
As always, we will continue to update any changes to this or any other developments as they occur.