Passing a contextual filter value to a view via a link with entityreference prepopulate?
One solution would be to add a custom panel to a panel page overriding the node edit form.

To do so you'll want to go into Panels Page Manager (/admin/structure/pages) and enable node_edit adding a variant that uses context to evaluate Node: type where Node being viewed is type "Your Content Type"

Then go into the panel page content section and choose "New Custom Content" from the panel selection dialog.

In the dialog that opens, makes sure to choose and input format that allows hyperlinks.

Make sure "Use context keywords" is checked and in the substitution choices you'll see %node:nid

You can use this to build the url:

&lt;a href="/node/add/reply?field_reply_orig_node=%node:nid" title="Add Reply&gt;Reply&lt;/a&gt;