My understanding of IDK option is “I don’t know if this location is safe” or “I don’t know if the information is accurate” or “I don’t know if this is a good place to exercise”. If you don’t know what you should do with spelling and grammar errors, maybe we should ask Niantic for a clarification in Criteria Clarification Collection - Discussion.
We are told to give thumbs up for correct spelling and grammar, so I believe it matters, even though we aren’t explicitly told to reject incorrect spelling or bad grammar. My guess why we aren’t explicitly told that is because it could be one spelling error or a missing comma in a long description (which most of us would be OK with), or it could be 1/3 of words in title and description misspelled in a really weird way (like with “pocknic”).