I may agree It's not the best but most of the time , It's pretty good way as most of the spammers out there write short posts.
excellent post quality (90%) = 1.05 (+5%)
good (80%) = 1.025 (+2.5%)
fair (70%) = 1.00 (+0%)
poor (50%) = -1.025 (-2.5%)
very poor (<50%) = -1.05 (-5%)
If you want to take a look at the source good and the algorithms on how all this is calculated then you may want to check the Github repo : https://github.com/achow101/BitcointalkAccountPricer
As for the price , people don't really follow it that much but they do use it from time to time.
Don't you just love how they value quantity over quality ? I know 75 characters is not much, I don't even think it is a line but still. Someone who send a short sentence and a link is way more helpful then someone who prattles on talking to themselves or whatever xP