That’s attributable with the right warrant and correlation with other data available to the ISP.
CGNAT is not an anonymity mechanism – at best it may be a very crude one, but the carriers will make extra effort to remove that anonymity through logging, retention, and segmentation.
Some mobile users can post but I think they've gone so far as to ban entire ISP mobile IP ranges to prevent people from constantly rolling new IPs on their phone.
Nice callback to Moot banning an entire Australian region (Queensland or Victoria, if memory serves) because Aussies did an outsized share of shitposting, and of Aussies those particular ones were the worst.
That’s true, but to be fair my original comment also said posts would be reliably associable with other posts from the same IP. With CGNAT, that association will be slightly less reliable, but not meaningfully so. The segment of the population who posts on 4chan is so low that there is negligible chance of two 4chan users sharing an exit IP and time window. Even with non-overlapping time windows, the population will be low enough for stylometry (and other factors) to remove any remaining ambiguity.
CGNAT is not an anonymity mechanism – at best it may be a very crude one, but the carriers will make extra effort to remove that anonymity through logging, retention, and segmentation.