Well, it's possible to detect patterns and characteristics in the language used in the comments that can provide clues about their origin...
Here's some indicators that a comment may have been generated by an AI system:
* Repeating phrases or sentences
* Using generic language that could apply to any topic
* Lack of coherence or logical flow
* Poor grammar, or syntax errors
* Overuse of technical, or specialized vocabulary
I mean, these indicators aren't foolproof... and humans can also exhibit some of these characteristics. It's tough to be sure whether or not a comment is generated by an AI system or not...