They just keep taking on different IP addresses until they find one that works. I actually built a system that auto-detects spam accounts and blocks their IP, but they change IP literally every single request, to a completely different IP in a different country. It's indistinguishable from regular traffic, especially since so many saidit users use vpns. It's a good idea, but at best it would only reduce the spam by half at most, and probably only for a few months until they find IPs that work and then it'll be back to normal. I used to block huge IP ranges and whole countries back 4 years ago or so, but it literally did nothing after a few days. The person or group generating most of the spam can mimic any IP address, they're not just using VPNs. Literally the only solution seems to be to look at what they post and ban them for that, but that's exactly the game of whack-a-mole we've been doing for months.

Most forums get around this by having paid staff that reviews all new things posted and they hand out user bans constantly. We have volunteers working at their leisure... which means we will never be able to control the spam unfortunately. It is what it is.