A highway, a building or a border should not share nodes with each other or other features. When it happens accidentally, you can use the disconnect option ("D") in the iD editor to 'unglue' the nodes from each other (nodes that are shared are grey instead of white). To avoid it happening, hold the ALT key down while you are placing a node near another building, it will prevent nodes from snapping together.
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            #REVIEWED_BAD #OSMCHA
            Published using OSMCha: https://osmcha.org/changesets/164092314
            