There is no hard and fast rule here. I think you need to handle these things on a case by case basis. 

**If the comments are closely related to the original question** and you have the capability then by all means edit your answer to cover the new feedback.

 **If they seem unrelated or beyond the scope of the question answered (or your ability to answer)** then you should certainly suggest that they open a new question to cover that topic or point them toward an existing answer that covers their concerns. 

I would **[hesitate to involve the mods](https://meta.askubuntu.com/questions/16900/questions-with-embedded-answers#comment34508_16901)** on anything similar to the aforementioned. There's no point in adding to their burden with something you can easily [handle yourself or with the help of the community](https://meta.askubuntu.com/questions/16900/questions-with-embedded-answers)

**If the comment could be construed as rude or offensive, too chatty, or non-constructive**, then yes by all means involve the moderators, if not you can certainly take one or more of the actions mentioned above to help the member reach a solution. Of course my slant on this is doubtless clouded by the fact that I'm actually [eager to help.](https://meta.askubuntu.com/questions/16264/are-we-truly-eager-to-help) Others may take a different view.