it's not doing its it's

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Every time I have sent student writing through with common homnym errors, it catches every single one.

are you using the free version or the subscriber version?

I can understand why vernacularized and slangy texts are going to meet up with a lot of false-positives, but I assume it would not take much logic to fish out that an 'its' followed by a 'not', as in the text below, would not in most cases be possessive. 

text-for-correction

No, I don't know her personally. I seen her around the gym the last few weeks — not that I think she works out that much — they say she don't work out much. But she has been hanging around and chumming up with the VIPs and the hot shots here in Vegas. And I seen her fight. On the tube. It's unavoidable 'cause she’s major, you know. But its not like I'm studying her, charting her moves or bullshit like that. I know how she fights. She fights like all the rest of them.

Same-same here - with "Its you"

text-for-correction

No, not any more, 'cause people eventually get tired of anything and the ratings were dropping and the sport was going to pot until you Chinamen came along and we got a new market. For all I know, maybe you Chinamen aren't feminists at all. Maybe you third-worlders just enjoy seeing us first-worlders kickin' the shit out of each other. Its you folks who run the show now. You got the money. You got the power. We've gone to pot here. And if that makes for good entertainment for you people, watching us going to pot? Be my guest.

Sorry for posting in the wrong forum, but I did so via a prompt from the program that perhaps should point out the distinction.