I think this is barfing on a lack of punctuation.
"this is the most shittest game online ever full of little nooby kids" (taken from a youtube comment) is "not likely stupid". Add a period at the end, though, and it works.
Maybe the parsing system isn't designed to handle incomplete sentences or sentence fragments? That could be difficult but key; many of the bottom of the barrel posts on the internet have no punctuation at all.
Update: Starting to really take an interest in this. While there are false negatives, I can't seem to find any false positives.