However, back on Sustainability.SE, the answer has this notice:
This answer is hidden. This answer was deleted and converted to a comment 1 hour ago.
The answer was not converted to a comment, it was migrated and then deleted. The post notice should simply stop after "This answer was deleted."
I confirmed on several other migrated questions with on Sustainability.SE that that same post notice occurs: here, here, and here. I don't have enough rep anywhere else to see if this is happening on other sites.