That's customizable isn't it? When I text I'd much rather have emoticons than a newline, whereas it's opposite with emails, and I've found that Swiftkey does a good job switching between them (somehow).
To my knowledge, there isn't a setting that changes it, but if you know of one, please let me know! I tend to send pretty longform texts to my girlfriend, so it's a bigger deal to me than probably most people.
Of course, recently we've been using Whatsapp instead and that works perfectly fine.
