Hi,
it has been frequently requested that there should be a way to contact anonymous users. In the past few days, I've hacked together a solution for this. It requires that you run patch-usernewtalk.sql and there's also a couple of new texts to translate.
It works as follows:
1) In the recent changes list (both normal and extended), there's now a "Talk" link, both for logged in and anonymous users. (This was necessary because the link for anons goes to their contribution list, which is useful, but from there you can't get to the talk page.)
2) Anonymous users also get the "Talk" link in the upper right corner. They don't get a user page link (let's not give them too much).
3) When a Talk page of a user is changed, a row is inserted into the newly created user_newtalk table. If it's a signed in user, the user_id column is filled with is ID, if it's an anon, the user_ip column is filled with his IP address.
4) When the Talk page is changed, instead of the "*", there's now a "You have new messages" link next to the "Printable version" link. (Our top bar is cluttered on low res, I agree, but I'd rather put "Printable" on the bottom and omit the top "Older versions" link.)
5) When the user visits the Talk page, the row is removed from user_newtalk.
6) A text is automatically appended to talk pages for anonymous users (which are identified using the \d{1,3}.\d{1,3}.\d{1,3}.\d{1,3} regex pattern) explaining that the IP address may refer to several users, not just one, and encouraging users to create an account to avoid confusion.
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Numerous changes had to be made in particular to User.php; patch-usernewtalk.sql creates the new table and removes the user_newtalk column from the user table.
I tested as much as I could, but I would appreciate if this could be put on test.wikipedia.org for some testing, preferably before the next accidental update.
All best,
Erik