Update fp-016-maintenance.md summary fix & header standardization (#2890)

Author: nataled

principles/fp-016-maintenance.md

@@ -8,22 +8,25 @@ title: Maintenance (principle 16)
 
 The wording of this principle is still in progress.
 
-## Summary and Purpose
+## Summary
 
-The ontology needs to reflect changes in scientific consensus to remain accurate over time.
+The ontology SHOULD reflect changes in scientific consensus to remain accurate over time, and MUST be responsive to community requests.
 
-[This check is automatically validated.](checks/fp_016)
+## Purpose
 
-## Implementation
+## Recommendations and Requirements
 
 Ideally, the maintainer of an ontology SHOULD actively monitor for any changes in scientific consensus, but--at a minimum--the maintainer MUST respond to requests from the community pointing out such changes in accordance with the [Responsiveness principle](http://obofoundry.org/principles/fp-020-responsiveness.html). Tentatively, we consider scientific consensus to be reached if multiple publications by independent labs over a year come to the same conclusion, and there is no or limited (<10%) dissenting opinions published in the same time frame. In cases when an area remains controversial, and no consensus is reached, then it is up to the ontology maintainer to either leave out the controversial term, or pick a viewpoint for practical considerations, and note the presence of controversy in an editor note.
 
+## Implementation
+
 ## Examples
 
 ## Counter-Examples
 
 ## Criteria for Review
 
 The developers of the ontology need to include a statement specifying how they are planning to maintain the ontology. We expect that an ontology will be maintained for at least 3 years from the time of acceptance.
+[This check is automatically validated.](checks/fp_016)
 
 <Category:Principles> <Category:Accepted>