UPDATE: An issue for this fix has been released, so you should be able to see and reply to comments properly. If you have any issues, please send in a support ticket!
We are aware of some issues around replying to comments on stories, where comments are appearing posted but then are disappearing later when returning to the comment thread.
We really apologize for any inconvenience this issue is caused - we are tracking the issue and have raised it to our development teams to look into, so we hope to have it resolved soon!
We will post again as soon as we have a fix!
Thanks for your patience and cooperation with this,
The Wattpad Team