December 7, 2022
An answer, which was highly upvoted, has been recently deleted by a mod.
After searching briefly on the net, the content seems to be original and the author's explanation more than valid, which explains why it attracted 20 upvotes in the first place. The post contains no links, it doesn't cite any website or leading authority but there are also other answers without references and citations.
It could be the user, who is currently suspended, paraphrased an entire excerpt which leads to an interesting question: is content that has been sourced outside but bears little to no semblance to the original text, still plagiarism?
In the past, users–especially newcomers–who'd copied content from an outside source without attribution or using block quotes were given a second chance to name their source, and to correctly format their answer.
It seems this opportunity was denied to the user, and their answer was deleted.
Why was a good answer deleted when other answers have been left alone? Answers that were posted later, repeating more or less the same information, albeit a few with more detail. Only one of the answers actually includes a helpful link.
Has this deletion anything–I mean, is it in any way connected–with the ban of ChatGPT on Stack Overflow?
Use of ChatGPT generated text for content on Stack Overflow is temporarily banned.
[emphasis in bold mine]
The primary problem is that while the answers which ChatGPT produces have a high rate of being incorrect, they typically look like they might be good and the answers are very easy to produce. There are also many people trying out ChatGPT to create answers, without the expertise or willingness to verify that the answer is correct prior to posting.
As such, we need to reduce the volume of these posts and we need to be able to deal with the ones which are posted quickly, which means dealing with users, rather than individual posts. So, for now, the use of ChatGPT to create posts here on Stack Overflow is not permitted. If a user is believed to have used ChatGPT after this temporary policy is posted, sanctions will be imposed to prevent users from continuing to post such content, even if the posts would otherwise be acceptable.
I've only just unearthed this, frankly alarming, innovation.
9 December 2022
In the end, a total of seven answers were submitted between December 5 and 6, and each one was deleted on December 6. The answers were written in good standard English, nothing in them reveals anything suspicious except for their inexplicable deletion.
Four of the seven answers were for single-word-requests, one answered a transliteration question, and two were about relative pronouns, and meaning. Even though the answers were not copied from online sources, e.g Wikipedia, they appear to be generated by the AI chat bot known as ChatGPT. The answers were written very clearly, included detail, and sounded perfectly natural and very believable. There were no grammatical or lexical errors but they didn't cite any references or include any supporting evidence. However, I believe this will be an easy-enough obstacle to overcome for anyone looking to camouflage their A1 contributions. Consequently there are probably many other AI generated answers on EL&U that have slipped through the net.
UPDATE 2 (21 December)
So I discovered an easier method to track down deleted answers. Initially, I thought the user had only posted two answers, but upon further investigation I discovered twelve answers had been posted within a two-day period before the account was swiftly suspended. This sudden surge of productivity likely triggered alarm bells among the moderators, leading to the eventual announcement of banning answers generated by chatbots.