In the planning phase, I'd say getting an answer like "I like that!" or something similar to a detailed message I sent is a surefire way to deflate any motivation I might've had for a potential roleplay. I don't need a 1000-word response or anything, but just something to work with.
In RP, I don't think there's very many things that turn me off. Doing something that's clearly in my offs is a good one, but I've never had that happen. Probably controlling my characters would be the one thing.