I think what is happening is that they disappear when you select the 'view all comments' option. We have a ticket to get this fixed. It should be resolved on Monday night so that the comment responses are always visible. It's something like that. And our team is working to make it so they always appear. 

I have noticed that as well -- disappear then re-appear ---- a glitch, I presume.

Roger D. Mucci that happened to me on few occasions - so I prefer the original method of leaving a comment.

Now in Q&A section, I cannot have two answers so the only way is to edit my comment or add comment.