Hi David,
In some areas, OpenStreetMap data does have fences included, whether these are derived from Bing, surveys or other sources. oomap (
https://oomap.dna-software.co.uk/) uses this data, and optionally will render fences. In some instances these can be useful but as you have found, in well-mapped urban areas these can dominate and add far too much clutter.
The problem has been more visible recently as I fixed a bug in oomap where fences weren't rendered regardless of preference. To turn off fence rendering, check out this guide:
https://oomap.dna-software.co.uk/help/details/rendering-options/...and uncheck the "show fences" option.
These options are not remembered between sessions so you'll need to adjust them on each noew occasion.