Post quality should not be determined by just the size of your post. The only reason it is done here is because that is the easiest way to gauge post quality, but it is most certainly not definitive nor accurate.
Now I understand why some Gonzos here do full quotes of long posts only to add a "Well done!" or similar.
I'm sure you will find a better algorithm yourself, but in case you'd like some input, feel free to PM me. I have done some "text quality metrics" in the past, so maybe you could get some inspiration from that.
Rico