simply have wait period of 24 hours with any new signups before they can post threads
heres one i nba betting forum https://www.covers.com/forum/ViewThread/103429564/11--4-5-k-plays
We have 24 hour period before posting / creating a thread already in place and we are also enable to block IP addresses as well but the users can simple use a VPN or change their IP address to get around this.
We are evaluating different options to combat this one of which is to manually moderate the first post or thread or use machine learning to look for certain keywords and automatically remove and block the user.
Hope to have something for you guys here soon as we can relate to how annoying this can get for everyone.