Talk 2.x allows:

Please, note that inserting links to attachments is available from version 2.2.0 only.

Inserting links to Confluence and external pages to comments

To insert a link to a Confluence page, do the following:

1. In the comment text box press [.
2. Start writing the Confluence page title.
   
3. Choose the page suggested by autocomplete.

To insert a link to an external page, do one of the following:

• Paste a URL to a comment. In this case, you will see the complete URL in the comment.
• First, select existing text in a comment and then paste a URL to it. The selected text is automatically converted to a link title.

Inserting Links to Page Attachments

You can add links to all types of file attachments supported by Confluence by dropping them in a comment. The file is automatically attached to the current page and its link appears in the comment as show below: