You are correct GME has been on the NYSE Threshold list since 09/22/2020:

https://www.nyse.com/regulation/threshold-securities

It's still on the list.

You are only supposed to be able to hold naked shorts for "13 consecutive settlement days".

SEC doesn't actually do anything. Failures to Deliver for GameStop stock has been on the securities threshold list for more than a month and off and on for the past year. I believe OverStock was on it in the past for over a year at one point and the SEC did nothing.

Right, but it must have been happening anyway, because there’s more shorts than shares available to buy. (I think?)

Wrong, see Matt Levine's explanation of this from today: https://www.bloomberg.com/opinion/articles/2021-01-25/the-ga...

> This does not necessarily mean a lot of people are doing evil illegal nefarious naked shorting! Really, I promise! There is no special limit on shorting at 100% of shares outstanding! Here is an explanation of how options market makers (discussed below) are allowed to short without a locate, but I want to offer an even simpler explanation. There are 100 shares. A owns 90 of them, B owns 10. A lends her 90 shares to C, who shorts them all to D. Now A owns 90 shares, B owns 10 and D owns 90—there are 100 shares outstanding, but190 shares show up on ownership lists. (The accounts balance because C owes 90 shares to A, giving C, in a sense, negative 90 shares.) Short interest is 90 shares out of 100 outstanding. Now D lends her 90 shares to E, who shorts them all to F. Now A owns 90, B 10, D 90 and F 90, for a total of 280 shares. Short interest is 180 shares out of 100 outstanding. No problem! No big deal! You can just keep re-borrowing the shares. F can lend them to G! It's fine.