maxerickson has commented on the following diary entries

Post When Comment
Targeting inappropriate 'layer' entries. 8 days ago

Keep Right reports some similar things (not sure what it would do with -5 with no other tag):

Building not visualized. Weird mistake! 3 months ago

I got here via

The building in question had an error in it's geometry. The validator in JOSM was able to detect it, there was an extra node on one of the corners. I just merged it with the corner.