A recent survey conducted by Zoosk revealed that for 72% of people who use online dating sites (like, for example, Zoosk), poor spelling and grammar are deal breakers. These errors are a problem not necessarily because they make the writer look dumb, but because they make them look lazy or indifferent. And that's not the message a person should be putting out when they're trying to find a date, even if it happens to be true.
And yes, punctuation counts. Of the 9,000 people polled, 93% said that just adding a period at the end of a sentence makes their opinion of the person sending the message more positive. So if you proofread more, you'll get rejected less.
The good part of this news is that grammar and punctuation are things you can control. Unlike your looks or, god help you, your personality. Best of luck out there, people.