I'm having a hard time finding a use case for the "very low quality" flag that isn't already covered by some other flag. The descriptive text for VLQ basically says that it's for cases where no amount of editing can salvage a post, no matter how intrepid the editors are.
In 99.9% of cases, that translates to "we can't tell what this person was trying to say. Even if we squint and tilt our heads."
Incomprehensible questions can also be described as "not a real question" or "not constructive." Users can already flag or vote to close as one of those two, depending on rep.
Incomprehensible answers can also be described as "not an answer." We already have that as a flag option, too.
In the other 0.1% of cases, a question might be just coherent enough to be understood, but show a complete and utter lack of effort. NARQ would apply there, too.
So do we really need VLQ as a distinct flagging option?