One of my edits received the reason 'Park added by new user'. This is the feature: https://osmcha.mapbox.com/api/v1/features/51823610-way-522248725/
Maybe it was caused by an error in the osm-comments API. Take attention to the first edit date of my user in the feature properties: "osm:user:firstedit": "2017-09-07T20:03:33.648Z", but my account was created in 2010.
Another experienced user, filed an issue with a similar error with the 'Pokemon nest feature added by new user' reason: OSMCha/osmcha-frontend#193 . If you check the API details of the user, it also has a wrong first edit date: https://osmcha.mapbox.com/api/v1/features/51824005-way-505801852/