So, I'm heartless for being gramaticly correct? Hm... Kind of an interesting topic. I can see where it gets that. But it depends on what you're saying. Is it one word phrases? Like "Okay." "Sure." "Neat.". Then yeah, that looks pretty "heartless". I'd prefer the word passive or just serious, you could say.
When I text, I find myself using periods around people I don't really know, find intimidating, or think is better than me. Like, I managed to find Cowmeat on FaceBook (don't ask), and I found myself using periods more than not at all when I speak with him. Yeah, there was times I didn't use periods, but I did use them more often than usual. But when I speak with close friends, I use shit tier spelling and word flow.
So, back to this. I don't believe this study be accurate with how it tries to say we are heartless or something similar for doing so. Some people just prefer texting with good spelling and punctuation. Just an OCDC thing I believe.