I use 'unclear what you're asking' if I have to leave a comment that's more focused on 'what's your goal, what are you trying to achieve, what are you actually asking'...
I use too broad when I need to write a comment asking for more details, location information, information on what's tried. Or if there are several questions in the body, some of which aren't fit for IPS (Should I X? Can you tell me how to handle Y? in one body for example)