Hi user_5359, 

Mapillary is a Swedish firm developing blurring software for faces and other GDPR-sensitive elements on photos; 
they accept OSM contributor's photos to train their algorithm; 
they also recognise traffic signs and make those detections available to various routeplanners. 

Looks like the workings behind the tag in the iD editor to enter the photo reference were changed w/o alerting users. 

The 'share this image' link on www.mapillary.com/app looks like https://www.mapillary.com/app/?pKey=1094850792170039, 

Why this got mangled?   

Have again added tag=Mapillary and copied the share this picture link from the Mapillary website. 

Thank you for picking up, as it is always harder to retrace steps when asked years later ... 

Met vriendelijke groet (Dutch for 'with friendly greeting'), 
Hans 