What a mess these phones & texting have made of the social world. I'm so sorry to hear about your distress. I've experienced similar behavior. It is mystifying at first. Finally I came to the realization that conversation texting, for me, just doesn't work. So I do it the old fashioned way and call.

Quick texts as a "heads up" or "hey can you talk?" are different, but nowadays people ignore texts and emails. It's totally changed social norms. People just aren't aware how rude they are. Plus, because phones are nearly tethered to many people now, that fact presents a sense of urgency for all messages and a greater emotional impact when they go ignored. Basically people not responding to messages says to me, "you're not as important to me then this other stuff I'm doing". Am I the only one that feels this way?

If there's a way to turn off the "read at X:xx", do yourself a favor and turn off that notification. And call them once, if they don't pick up, leave a message and then the ball is in their court. I'd rather have one good, reliable friend than 100 fake people that ignore me in favor of getting more likes on farcebook