Let's say I have a web page with user-contributed content, which is good content but with bad grammar, slang terms, inappropriate tone.

I know that bad grammar is a also a problem because it drives away visitors and scares people from linking to it, but let's put that aside.
Let's also put aside the fact that incorrectly spelt terms might be ignored by a crawler, potentially leading to less text-comparizon hits.

QUESTION: Do search engines like Google directly recognize and penalize bad grammar?
For instance because they might consider bad-grammar as a sign of low-quality content.