Cato, a checkuser on the English Wikiquote, was revealed to be an account operated by the sockpuppeteer Poetlister (also known under various other names, including Runcorn). After some investigation to conclusively prove that the accounts were related, its checkuser rights were removed on 6 September. FT2, who led the investigation and requested that the rights be removed, stressed that the checkuser rights had not been abused.

In May 2007, the Arbitration Committee banned Runcorn, who was then an administrator, for extensive sockpuppeting across multiple accounts, dating back to 2005. Some users were skeptical of the findings, and Poetlister vocally denied any connection to the other accounts. Poetlister remained a sysop on Wikiquote under that username, as no sockpuppeting had been alleged there. The user later became a bureaucrat there, and an administrator at the English Wikisource.

In May 2008, Poetlister's account was unblocked, after a community discussion in which Poetlister was deemed to have "reformed". Having been unblocked, it was occasionally checked for possible repetition. Evidence emerged showing a possible sockpuppet on English Wikipedia, so the suspect account was checked thoroughly. A cross-wiki checkuser showed that the account was likely also Cato, an administrator and checkuser on the English Wikiquote.

After this was discovered, secretive investigations continued on the Cato account and others involved in the sockpuppeting, and the Wikimedia Foundation office was notified of the situation. Cato's checkuser actions were monitored by another Wikiquote checkuser; throughout his time as a checkuser, only one action, the check of one of his own sockpuppets, appeared illegitimate. While Cato's OTRS access was terminated, his checkuser access was not yet removed, because it was determined that abuse was unlikely as long as the investigation remained private.

Upon learning that the matter had begun to become public, and Poetlister began requesting to have his accounts renamed, FT2 had Pathoschild, a steward, terminate Cato's checkuser access on 6 September. FT2 then made the investigation formally public, posting an explanation of the incident as a request for comments on the Meta-Wiki.

The explanation drew support from many users involved in the case, including Wikiquote checkuser Aphaia, English Wikipedia checkusers Jdforrester, Sam Korn and Jpgordon, Foundation representative Cary Bass, and Jimbo Wales. Wales said, This incident has affirmed my trust in the processes at en.wikipedia and I hope that we will see some strengthening of standards at en.wikiquote. This is not a criticism of en.wikiquote, to be sure. It is a small project and therefore more informal.

On 13 September, Cato admitted sockpuppeting, in a statement on Wikisource:

I have used a variety of names on different Wikis. The following are cross-wiki (including ones created by SUL but never used), but the unattached ones are not me.

[Bedivere, Cato, Londoneye, Poetlister (some accounts renamed to Quillercouch), Runcorn, Whipmaster, Yehudi, and Crum375, an impostor account on Wikiquote]

The following are on en:wp with no SUL:

[Brownlee, Habashia, Holdenhurst, Newport, Osidge, R613vlu, RachelBrown, Runcorn, Simul8, Taxwoman (also on Commons), and Wqlister]

This list is as complete as I can make it; I have double checked and believe that there are no omissions. I sincerely and thoroughly apologise to everyone and beg their forgiveness.

While the checkuser right was removed, the accounts' administrator and bureaucrat tools were left intact, and the individual communities were given the opportunity to discuss whether those accounts should retain any rights, and whether they should be blocked or banned. On both Wikiquote and Wikisource, votes of confidence were started to see what, if any rights the accounts should retain. As of press time, both communities had nearly unanimously agreed that all accounts should be stripped of their rights. However, the question of whether the user should be banned or not was much more split, with neither community having reached a decision. As of press time, all accounts still retained their individual privileges. On Wikipedia, however, where Poetlister had been banned previously, the ban was quickly reinstated.