The post quality monitor is a huge asset, as it will tighten up the standards and possibly encourage the shiftless and lazy to take their skills elsewhere until they come closer to par.
Revising these seems sensible. I think the problem is that incomplete sentences is only one of easily a dozen triggers that could awaken the message prompt. In fact, run-on sentences (overly-complete sentences) are more likely until we restore some punctuation habits back into our upcoming generations.
Either a more generic suggestion or a list of triggers in the detection code would make more sense than that one shot in the dark.
Perhaps…
“Body seems unclear. Can it be improved?”