ArcGIS services with Leaflet: Callback behaviour with GeoJSON reponds

[AndryJoos]

Hey CH-GeoDevs - we just stumbled upon a problem with using Leaflet together with ArcGIS services. My colleage Tobias posted it in the ArcGIS Rest board (see Request featureservice with f=geojson & callback parameter in onpremise installation ).
I intend to drive a bit of attention to it by re-posting it here and at the same time hopefully give a bit of activity back to the GeoDev Switzerland board Thank you and greetings!