Yea when I saw the attack last night there were no admins/mods (that I know of) online. So I report one of the spam post hoping some email notif will fly out and find you guys.
About anti spam tactics, honestly, it's not as crucial to keep it a secret and not discuss it publicly. 'Security through obfuscation' never works. In the net it's all transparent. With heuristics and network any bot can retry, disperse and retry again. Captcha works. If you need anything more sophisticated than that, then this must be a CIA forum or something and spamming would be the last of your concern.
By the way it looks korean but on my mobile at least some japanese hiragana are mixed up as well. Dunno why.
Edit: it doesn't have to be captcha. One of those 'I'm not a robot' checkboxes is fine too