The problem

A new user accidently added addr:city and addr:province tags to a large selection of objects, including rivers and individual nodes.

Changeset | Diff

The user mentioned that the tags were intended only for buildings, so thought I would document the cleanup for future efforts like this.

Finding all the problematic data using Overpass

It is possible to extract all objects with addr:city added by the particular user using this Overpass query.

Resulting features

This data can be exported into JOSM via remote control for further inspection and cleanup.

Fixing data in JOSM

Once all the data is loaded, we need to select only those objects or features that have been incorrectly tagged with the addr:city and addr:province. Since we know that the tags are valid on building ways, we will use a filter to select such tags on anything that is not a building way. We can use the find dialog (ctrl+F or cmd+F) to look for exactly this.

Find all objects tagged with addr:city and not a building

This selected 3,989 objects from which the tag can be deleted. Just select and delete the tags.

As a bonus got to also cleanup duplicate nodes using the validator.

Upload with a descriptive changeset comment and all done!