Note: Banner taken from Googling the tread title and finding a TV show by the same name.
Alright, I had a joke-y conversation today about Vegans being undateable and just living life wrong (they are, there can be no argument here!). That got me wondering what specific things or traits would turn somebody "undateable" to me. So I figured what they'd be for other people, and how different preferences (or dealbreakers) contrast.
If possible, stay polite. Your picks for undateable things may well be insensitive, offensive or whatever - and I ask others to respect that and not attack users over them! - but you can almost always state them in a decent manner, or at least wrap them in humor somehow. Don't be an utter douchebag about things.
Keep in mind that you can use markdown to make lists by putting a " * " in front of an item and ending the line with two spaces, repeating it per list item. It helps.