TheRealSaxman - 1:32 pm on Mar 29, 2013 (gmt 0)
Didn't have time to read EVERY word of the article, but I find it funny that that the article title says "NEGATIVE KEYWORDS DO NOT AFFECT GOOGLE ADWORDS QUALITY SCORES"...yet the final comment by "Google Adwords Help" says..."Matthew Mierzejewski has also written a fantastic post on this topic and detailed how negative keywords impact Quality Score."...hmmm? Two articles that contradict each other? There wasn't a link to the latter so I could read that article...just found it humorous.
Taking all this in, and reviewing the original question again from chewy, I'm still of the belief that even though the QS of broad match terms are based off of it's exact match we would still see a slight increase in QS, OVER TIME, as our CTR would get better as we continue to add negatives as this would, as chewy stated earlier, "lower inappropriate impressions".