# Is there a way to @ exactly one of two users whose names differ, if at all, only by whitespace?

I recently approved an edit to Zeroes of characters of general linear group induced from certain characters of parabolic subgroups by user @math seeker. I approved the edit, which was otherwise excessive, because I thought it was by the same person who had asked the original question, @mathseeker. (It struck me as strange that such an edit wouldn't be automatically allowed, but I thought maybe new users had a different experience.)

Having discovered that these users were potentially different, I left a comment to the editor letting them know that, if they were not the same as the author of the original post, then the edit was excessive.

All that background is not the question. The question is as in the title: how, if at all, can one @-notify exactly one of two users whose names differ only by whitespace? (In this case it doesn't matter, since one not only need not but can not @-notify the asker, but the question makes sense in other circumstances.) I guess the question can be asked more generally, e.g., for users that have identical names, not just identical-modulo-whitespace names.

• One option (this would need testing) might be to use the @-mention and just have the part of the username before the whitespace. For instance, I have always operated under the impression that @firstname would work when the username is firstname lastname. But then this raises the thorny issue of the other user, firstname othername.
– David Roberts Mod
Aug 3, 2022 at 8:09
• In a comment, if I type @ and the first letter, then the system shows me a list of all users eligible for @-mention starting with that letter. I can click on the one I want. What happens in this case? Aug 3, 2022 at 10:29
• @GeraldEdgar, re, I don't know. Unfortunately I can't test it in the post in question, since neither user pops up in the @ autocomplete. Aug 3, 2022 at 13:26
• @DavidRoberts, I had always thought that, in that situation, the system simply dumbly notifies the alphabetically first user (which I guess would mean the one with the space?). But that is not based on much evidence. Aug 3, 2022 at 13:26
• @LSpice The query which was mentioned in chat returns several posts where various users with the same username posted a comment. If you want to test this, maybe Gerhard Paseman or Gerry Myerson would be willing to help you. (Or maybe somebody would be willing to temporarily change a username - but one should keep in mind that username can only be changed once in 30 days - IIRC the limit can be overridden by moderators.) Aug 3, 2022 at 15:41
• @MartinSleziak, thanks! I guess, with Gerhard's and Gerry's consent and participation (or of course @‍GeraldEdgar's, who is already here!), I could test "@‍Ger" in an appropriate thread and see who receives it, but I am reluctant to play around in "live" areas with people who haven't agreed to test this out, especially since it's non-urgent. Aug 3, 2022 at 18:28
• @GeraldEdgar, on further thought about your question, if the usernames are distinct after stripping whitespace, then the system will auto-complete to the full-length name, and there will be no ambiguity; but I guess you meant what happens in a thread with two or more users who have the same name modulo whitespace. Aug 3, 2022 at 18:30
• Aug 4, 2022 at 4:41
• I have asked this question on Meta Stack Exchange: Is there some difference between typing a username and using the auto-complete? Some similar screenshots (and other comments) are posted in the MathOverflow chatroom. Aug 4, 2022 at 4:47
• The comment in Meta SE: meta.stackexchange.com/questions/380968 has a comment that asserts the most recently posting match is the one notified. Aug 4, 2022 at 15:16
• @Justin, I have done that. However, I think it might not be that useful, since a ping can never be addressed to the asker of the question (who is always notified)—but the asker will always get a notification of comments on their question anyway. Aug 5, 2022 at 15:25
• @Justin, OK. I will delete the comment. Aug 5, 2022 at 15:32
• @MartinSleziak: I was pinged on both accounts. Thank you for the (test) comment. Aug 5, 2022 at 17:08
• Somebody rang?? Aug 5, 2022 at 22:21
• @LSp, yes, indeed. Aug 6, 2022 at 2:51

Is there a way to @ exactly one of two users whose names differ, if at all, only by whitespace?
According to How do comment @replies work?, spaces are removed from the display names for matching purposes. So Jon Doe and JonDoe will both need to be referenced as @JonDoe (@Jon will also work). So who gets notified? According to the same FAQ on Meta SE, matching is performed in reverse chronological order. Hence, the Jon Doe who commented most recently will be notified / pinged, whether you manually type the username or use the autocomplete options. This is also the case with usernames that are exactly the same (with no whitespace, etc.).