Hi Andy,
We also use Mapbox, and by using a combination we can usually make improvements to these islands regardless of potential Bing offset. Alternatively we make the decision to not make any edits in an area (we do this often). Can you point me to some of the worrying changes? I can always fix them if you let me know.
Thank you for the comment,
James

Hi Andy,
Thanks for the comment.
https://overpass-api.de/achavi/?changeset=47898820 
I think that this small island looks better now due to these changes. Do you know if Bing is offset here? It would be great to know for sure, but until then this feature has been improved significantly according to what Bing currently shows. There were only 6 nodes on the way before this changeset. 
Thanks again,
James

I found this island through a MapRoulette challenge, I’m part of a small group who are attempting to improve the alignment of these islands using MapRoulette and JOSM.