That would be absolutely awesome! Especially if it’s not just words but also regular expressions. Auto-tagging based on regular expressions would bring tags in discourse to a whole new level!
Yes, and I also realize that the existing actions apply to posts while tags can only be applied to topics. So the question is: will tagging actions only be based on the first post? Or can any reply also trigger the tag? Or will it be a setting, whether it applies to both?..