At least for DDoS by attacker who use Tor network, it can be mitigated by enabling PoW feature.
Only for onion service though. Forum would have to have a onion version and Tor users have to surf using that only.How demanding is it to make an onion version of the forum? Considering that these attacks last longer and longer, it would be really good to have an onion version that, if I understood correctly, would be resistant to such attacks.
Onion version of the forum can only guarantee anonymity but will still be venerable of DDoS attack to an extent.
Again, I don't think that theymos will buy the idea because of the reputation of the forum. Having an onion version might take the government's eyes to the forum and some kind of legal compliances would be required.
Besides, running an onion version of the forum will require some more resources to reconfigure the server and secure same against attacks. I don't think we are committed to all these now.