My general rule of thumb on flagging is this:
Raise a flag if:
There is something that needs done to the question or answer that you do not have ability yet to do yourself.
You think there is something suspicious going on
Rudeness or bickering in the comments
Don't flag for:
Wrong answers, down vote instead
Low quality answers, down vote instead, or try to see if simple edits to the question or answer make it better, for instance copying relevant pieces of information from a linked article that the author might be referring to