From the AMO addon page:
The "Support Link" redirects to:
which returns a HTTP 404 error. Seems the link should instead be:
While the AMO "Support Link" property might exist outside of Github (it does not appear in the packaged extension), this should be updated regardless...
I have fixed AMO and pointed the support email address to our public mailing list.
Not sure what you mean by the extension, but there is no support element available in the install.rdf. But there is a homepage one which we could use to point the user at least to our project page.