We should consider documenting the behavior of mongod when users manually tamper with the system.views collection. I'm not sure if this level of detail is appropriate for the manual, given that if users follow the rules and don't touch system.views, none of this should be a problem.
Here's the behavior: as of release 3.4.0, users who insert invalid documents into system.views will cause all views-related operations to fail on that server. It also prevents running listCollections. Operations performed through mongos, even when not run on a view, may fail because mongos will try to run listCollections.
I'm fine if we don't document this, but we should ensure that there's a note in the views page that says "don't mess with system.views".