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When I look for stuff on CL (I've been boat shopping in the Pittsburgh area for over a year now) I steer clear of posts without pictures. Honestly if the seller cannot be bothered to post a picture of whatever they are selling, they probably aren't 100% willing to sell or negotiate a fair price.

Sellers in general without pictures should be steered clear from, but I would guess that sellers with expensive things such as cars, boats, etc. have more reliability.
 
It really bugs me when people don't remove posts after selling the item and/or not emailing back to let one know the item is no longer available. I would really like to see an option to flag for bad grammar. It wouldn't have to remove it, just put a little flag next to the post that warns you of bad grammar. It would be kind of funny, actually, but impractical, since most would fall into that category.
 
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