This may apply to plone.app.discussion in general! so the ticket should be transferred!
Symptoms
When trying to add a jquery ui based validator to the comments custom_name field I discovered that the possible multiple instances of the input form share the same DOM object IDs.
That object occurs at the main position and also shows up with identical ID at the answering location result in serious issues when adressing the field for validation bling bling via javascript.
Since the form is rendered elsewhere, it is hard to fix this in this fork without overriding plone.app.discussion.
Suggestion
The javascript used by plone.app.discussion that makes the answering input appear, should be responsible to remove or change all other instances in the DOM. Making invisible may no be enough!
IDs shoud be unique!
Suggestion: use classes instead and add the comment id as DOM ID