Grammar does make a difference in your SEO work. It does make an even greater difference in your conversions.
From the search engine’s “point of understanding” it matters. And yes, many search engines to have a sense of understanding in a form of intelligence (which is artificial intelligence or AI.)
Some search engines like Google have been able to “understand” the context of a message for some time now. Writing a better quality of content will help you much more…
“then if ya right very week copy ful of speling errors and porly strucured sentances.”
or how bout…
“Why don’t you throw your Father down the stairs his hat when he asks for it?”
Also Grammar can impact Conversions….
Where grammar makes a difference to conversions is in sales letters or where you are trying build credibility for a product. It matters to the engines and it matters to your customers. Using poor grammar may cost you more than you realize.