I typically do this to save space. At least the expectation is set - the person has to click on the 'said' link to view the whole post. That way, I'm not attempting to misrepresent the post. The only time I will leave a partial paragraph or sentence, is when I want to address a specific point. But I'll rarely cut out more than a sentence.
I find that so sad tbh. I've seen people try to attack my arguments by highlighting how I've failed at my grammar. But that's rare. Those that do, have usually misunderstood what I said because I proofread every post.
People also need to remember that not everyone's first language is English. Sometimes, when you correct someone's grammar, it can send the message of "you didn't have proper grammar, therefore you're unintelligent" and that's sad. Focus on the content and not minutia.