Does the mentioning of a user with an @ work across SE sites?

Question

I had somewhat too much time and after using a word in a post here on Cooking, I asked about its proper usage on English.SE. They happened to create an even better word/neologism for the situation, so I made sure to add it to my original post and to credit the English.SE user in a comment. I used the @ sign by force of habit, but that got me thinking: Is it doing anything? Will the user be notified of my comment, if he hasn't associated his English.SE account with Cooking.SE?

Answer 1

See the MSO FAQ How do comment @replies work? for more information on this feature. Specifically:

• The first author of the question or answer will always be notified of any new comment.
• You can explicitly notify one (1) other user, by using a @name syntax.
• Single trailing punctuation such as a dot, comma or colon is ignored, like @name, yes works, but @name... no does not.
• Things like @op, @downvoter or @all have no special meaning.
• If a user comments on their own post and there is only one person who has previously commented, then that person is also notified if @name is forgotten.

And also this bit:

Notifications apply to the author, commenters, and editors of the question or answer that you are commenting on—users not in that list cannot be notified. The question and answers are all considered independently. For example, if Alice was the author of, commented on, or edited the question or her answer, then you cannot notify her by commenting on Bob's answer (unless Alice also participated in that answer), and vice versa.

So in short, the answer is no, you cannot write @user anywhere and have it show up in their inbox. It has to be a reply to a comment they posted on the same answer (unless they authored or edited the post, and in the former case, the @name is unnecessary).