I wouldn't have thought there'd be a need to ask this as most places are set up so it's not possible, but we have old Matt *waves* and new Matt who seem to have the same name.

My reason for asking is I was replying to a comment to new Matt in a recent Question of his and it occurred to me that I didn't know if using @Matt would also target old Matt, which would obviously not be ideal.

  • Perhaps we should suggest that first name only identities add another letter such as first letter of last name. What are the odds we would still have a duplicate (1:26)?
    – Ashlar Mod
    Commented May 28, 2016 at 1:27
  • From managing all the accounts at my company i can tell you that adding only one letter won't give you that much more room to play with. There will always be collisions, especially when handling first-name-based usernames. I find it very curious that it's even possible to have two identical usernames in the same network...
    – Stoppal
    Commented May 30, 2016 at 6:11
  • ... should have looked that up first :( It's only the Display Name that's a duplicate. Could a moderator/admin enforce uniqueness of display names within one particular SE. It looks to me as if i can be Stoppal here, and SomeonesM0m in the EE-SE for example.
    – Stoppal
    Commented May 30, 2016 at 6:18
  • @Stoppal, I realise it's only the display name, the user ID# is unique in each case. But the @[username] function appears to target the display name only which is what I was checking on.
    – Graphus
    Commented May 30, 2016 at 7:19
  • @Graphus yeah i realized that too late, but making the display name forced unique for the WW-SE would fix that, hence my question if a moderator/admin could setup such a rule.
    – Stoppal
    Commented May 30, 2016 at 7:55
  • 1
    I am going to change my name to Graphus to hopefully got more upvotes
    – Matt
    Commented Jun 8, 2016 at 18:48
  • @Matt, well I tried to just reply with an LOL but <grumble grumble> apparently you can't post a comment that short.
    – Graphus
    Commented Jun 9, 2016 at 7:26

1 Answer 1


I know this is late, but, yes there can be duplicate usernames. By now there are 5 Matts on this site. When replying, the system knows which users are relevant to the post (i.e. they've answered or commented already). It will pop up with their name when you type @.

I'm not sure how it handles cases when two Matts have commented on the same post. I guess that would be pretty rare.

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