I haven't read the replies, so this goes directly to OP Milton: I had the same idea a few years ago, and I'm all for it. A specialist actually contacted me on one of my articles, but it was quite hard for him, because he had to switch to the article history, find my name, navigate to my user page, then google for my name, search for the e-mail address etc.
I'm open to debate the system for visitor comments. It shouldn't be a subpage or a second discussion page. This would be vandalized sooner or later, and it would divert energy for maintenance. So it could rather be an online comment/email form incl. captcha to send a message to an author, maybe via a CZ "constable office". There needs to be a spam filter nonetheless, and if the visitors actually enter the topic/article in the subject heading, the message is likely to reach the right author via a constable. Maybe we can also leave out the constable completely and find a fully automated system, like a pop-up menu to select authors/articles to contact/comment on. Such an automated system should also be able to check, if the email address entered in the online comment form is valid. If it's not, the message would be treated as spam.
Suggestion for a comment system:
(1) there is a "Comment" link in the left CZ column, e.g. under "Permanent link".
(2) Clicking it leads to a special CZ page, with an online email/comment form, containing:
(a) Subject heading 1: automatically generated from the referral, e.g. "RE: CZ article 'Biology'"
(b) Recipient 1: automatically generated, i.e. send one copy of the message to the CZ editor in charge of the article
(c) Recipient 2: one of the article's authors, to be selected by the anonymous commenter from a pop-up menu that
only contains the authors that actually worked on the article, sorted by the number and/or the scope of their edits, most active first
(d) Subject heading 2: topic of the comment to be typed-in by the commenter
(e) Field where the commenter needs to enter his e-mail address
(f) Field to repeat the e-mail address
(g)
Optional field for the commenter to enter his real name
(h) Text field for the message
(i) CAPTCHA
Send button. A copy of the message will be sent to the supplied commenter's email address. If the message returns with permanent errors, the CZ system will not forward the message to the editor and the selected author.