I thought this would be a useful thing. So I forked and patched the plugin myself.
Who knows if and when it will be accepted upstream.
Install it as a plugin:
rails_root$ script/plugin install git://github.com/EmFi/acts_as_audited.git
Usage doesn't really change from vanilla acts_as_audited.
acts_as_audited takes an extra option now. :require_comment, which if true, blocks creation, updating, or destruction of an audited model unless a comment is supplied.
To add a comment to an audit use model.audit_comment= "My Comment"
before create/update/destroy.
audit_comment can also be mass assigned making it simple to add a comment field to any form.
Before you can use my gem/plugin you'll need to update the audit table to contain a comment column. Sorry, but you're on your own for that, I haven't gotten around to writing a generator for it yet. If you don't mind wiping the audit table or don't have one yet, you can run script/generate audited_migration add_audits_table
(after dropping an existing audit table of course)
With my gem/plugin all that would need to change using your address example adding an audit_comment field to your form.
<%form_for @address do |f| %>
... standard address fields
<%= f.label_for :audit_comment %>
<%= f.text_field :audit_comment %>
<% end %>
EDIT: Now has a complete test suite.