Yes, SmokeDetector is active on Artificial Intelligence as well, and it's automatically flagging posts of which it's 99.75% sure it's spam. Fortunately, Artificial Intelligence doesn't see as much spam as the rest of the network, and only 117 flags have been cast last year. Most (all?) other bots in that blog post are tuned towards Stack Overflow content and can't be ported directly to Artificial Intelligence, though some of them might be after some adjustments.
If one decided to create a bot for accelerating moderation by flagging duplicates and off-topic questions, is that specifically allowed in the website? A bot that helps to automatically flag questions and duplicates may help a lot in removing and noticing unwanted posts and answers
Yes, that is allowed, as long as you don't do anything stupid. You need to be reasonably sure the flag accuracy is at least as high as the average human user (which is about 95% IIRC). If you get flag banned because of a bad algorithm, that's your own problem.
and with a machine learning algorithm one can classify it to a very high degree of accuracy.
Well ... that might surprise you. SmokeDetector relies heavily on old-school regexes. We've tried a few times to classify spam based on machine learning, and we got nowhere near the 95% mark, let alone the 99.75% needed for autoflagging. (That percentage is so high because validated spam flags carry a heavy penalty.) Determining off-topic and duplicate questions looks even more challenging to me, but I hope you can surprise us.