I can build on the nether roof.
Steps to replicate:
1. Get on top of the nether roof following a youtube tutorial.
2. Build farms, pathways, portals (anything you want) on the roof.
Expected result:
Inability to place blocks on the bedrock roof.
Actual result:
I can build anything I want.
Related issues
Comments

I would like to ask the devs why Java edition considers this as a WAI feature but not on Bedrock edition. How will you achieve parity with this?
This is a pre-existing problem and therefore does not count as a parity bug. Any behavior that is different and was introduced before Buzzy Bees is not considered a parity bug.
Thank you for your report!
We're tracking this issue in MC-180755, so this ticket is being resolved and linked as a duplicate.
That ticket has already been resolved as working as intended, which means this is not considered a bug and won't be fixed. Please do not leave a comment on the linked ticket.
If you haven't already, you might like to make use of the search feature to see if the issue has already been mentioned.
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