You mean like this?

(Logs) . . 00:46 . . Krenair (talk | contribs | block) (Previously blocked) (bot, bureaucrat, check user, administrator) User account TestT123114 was created by Krenair (test)
        IP: 127.0.0.1   [UA here]
(Logs) . . 00:46 . . TestT123114 (talk | contribs | block) (Not unified) was created 
        IP: 127.0.0.1   [UA here]

Rather this:

(Logs) . . 16:37 . . USERNAME (talk | contribs | block) (Blocked) (Locked) User account USERNAME was created 
        IP: [IP here]   [UA here]
(Logs) . . 16:37 . . USERNAME (talk | contribs | block) (Blocked) (Locked) was created 
        IP: [IP here]   [UA here]

I can provide the full details in private if there's a need for them.

I guess it makes it's own entry from the AddNewAccount hook with a potentially slightly different timestamp, no comment, no title, etc. with the assumption that the user was created anonymously... And then gets the useful log entry via RecentChange_save.

Change #1052759 had a related patch set uploaded (by Dreamy Jazz; author: Dreamy Jazz):

[mediawiki/extensions/CheckUser@master] Prevent duplicate account creation events in CheckUser entries

https://gerrit.wikimedia.org/r/1052759

Change #1052759 merged by jenkins-bot:

[mediawiki/extensions/CheckUser@master] Prevent duplicate account creation events in CheckUser entries

https://gerrit.wikimedia.org/r/1052759

@Dreamy_Jazz From Manual:$wgNewUserLog I tried the suggestion of adding $wgLogRestrictions["newusers"] = 'autoconfirmed'; to my LocalSettings.php. I created a user but I could not see this recorded in CheckUser. I assume because the user creation is not written to Recent Changes.

Is this something we need to support?

In T123114#10001616, @dom_walden wrote:

@Dreamy_Jazz From Manual:$wgNewUserLog I tried the suggestion of adding $wgLogRestrictions["newusers"] = 'autoconfirmed'; to my LocalSettings.php. I created a user but I could not see this recorded in CheckUser. I assume because the user creation is not written to Recent Changes.

Is this something we need to support?

I had not considered this. This shouldn't the case on WMF wikis, but I think we should still otherwise support it. We can probably fix this by still creating the private event if the newusers log requires a right to view.

Change #1055884 had a related patch set uploaded (by Dreamy Jazz; author: Dreamy Jazz):

[mediawiki/extensions/CheckUser@master] Create private create-account event if 'newusers' log is restricted

https://gerrit.wikimedia.org/r/1055884

Moving back to 'Needs Review' for review of the follow-up patch.

Change #1055884 merged by jenkins-bot:

[mediawiki/extensions/CheckUser@master] Create private create-account event if 'newusers' log is restricted

https://gerrit.wikimedia.org/r/1055884

Moving back to 'Needs QA' for QA to resume.

I experimented with different combinations of $wgNewUserLog and $wgLogRestrictions['newusers'] and creating accounts. I saw only one account create entry logged in Special:CheckUser.

One thing I noticed is that if $wgNewUserLog = false; or $wgLogRestrictions['newusers'] = 'autoconfirmed'; and I create a user while logged in as another user, the fact that the account was created by another user is not shown in CheckUser. I assume because cu_private_event does not record that information.

I set $wgLogRestrictions['newusers'] = '*'; and the result seemed to be all the create account events in CheckUser were hidden (except those in cu_private_event), hidden in RecentChanges and I got permissions errors when going to Special:Log/newusers. I don't know if that is the expected outcome.

I also notice that, while logged in as a temporary user, if I create an account the CheckUser create account entry does not record the temporary account that created it. I wonder if that would be useful information to know. But I also see we don't record this information on Special:Log either.