This question is also answered at the following Link: Chowning FAQ
Why did my comments disappear after the chown?
Please note that sometimes comments will move over a few days, or weeks after a video is moved to a different channel. The comments will sometimes arrive after the video moves.
This delay in comment migration usually happens to videos with thousands of comments, so if the chown is for a priority artist, be sure to manage expectations before the chown process begins.
When will the comments come back?
In the case that comments disappear, in most cases, comments will take a max of two weeks to move/reappear after the chown. If more than two weeks have passed and comments have still not returned, please contact Vevo content ops.
Can we do anything to make comments return more quickly?
The comments cannot be rushed back, this is a limitation at the YouTube level. Vevo Content Ops cannot make the comments return more quickly. Usually, comments return within 2 weeks of the video chowning. If it's been more than 2 weeks, you may contact Vevo Content Ops. Thank you for your patience!