I'm not sure if issues caused by manually resizing the window are considered as bugs, but this is a case that happens with orientation change so thought it's worth mentioning.
Tested with iPhone 5
Steps are:
1. Create a notice and set it to "Hide Below Narrow Width"
2. Hold the device in landscape mode
3. Open the site -> you should see the notice
4. Switch the device to portrait mode
The result is empty block with borders
Tested with iPhone 5
Steps are:
1. Create a notice and set it to "Hide Below Narrow Width"
2. Hold the device in landscape mode
3. Open the site -> you should see the notice
4. Switch the device to portrait mode
The result is empty block with borders