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How do comment replies work?

Ive seen a lot of comments where people put @name to specifically address a comment made by another user. What is the protocol for this? Is it used by SO in any way?

Should the full name be used after the @, or if its a multi word handle, is just the first enough?

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marked as duplicate by Jon Seigel, Shog9, Arjan, random Jul 22 '10 at 17:32

This question has been asked before and already has an answer. If those answers do not fully address your question, please ask a new question.

See meta.stackexchange.com/questions/43019/…. – mmyers Jul 22 '10 at 15:32

2 Answers 2

up vote 5 down vote accepted

Here is the blog post announcing the feature. All of your questions are answered there.


There are some rules, of course:

  1. This only works when referring to other people who have already commented.
  2. Your comment must include @username that you are referring to, where “username” is a reasonable match to the user’s current display name (as seen in the comments above yours).
  3. There must be a starts-with, case insensitive match of at least THREE characters to the displayname. So @a and @ab will never match anyone or anything.
  4. Spaces are ignored in the match, so if the person’s display name is “Peter Smith” then just use @peter to match, or @petersmith.
  5. Matching is performed in reverse chronological order, so if there are five people named “John” in the comments, writing “hey @john, have you considered apples?” will match the most recent John to comment.
  6. Only one person can be replied to at a time in a comment. The first one in the string wins.
  7. Users who have no display name set, whose faux-displayname is derived from their OpenID URL, cannot be matched.
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@Clark Do you like apples? – Peter Ajtai Jul 22 '10 at 16:44

I've found that this varies by user. Sometimes people use the full name, sometimes the first name, sometimes a shortening of the name (I get "eruc" and "eru" and even "e" sometimes), though a real shortening might not notify the user. This does seem to be the de facto means of addressing a previous comment, or the owner of the answer, or the owner of the question. As long as you don't change it to @jerk. :-)

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It needs to be at least the first three letters, so the people using just "e" are doing it wrong – Michael Mrozek Jul 22 '10 at 17:08
@michael: yeah, i've missed a couple... – eruciform Jul 22 '10 at 17:27

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