I once sent to the a person I know and whom I helped financially once to congratulate him on his new job, and he didn't reply to me, and when I asked why you didn't respond to my message, he told me "he didn't think he should reply"?!! It seems people have different understanding of what is appropriate and what is not via texts. I personally don't expect immediate response, but I expect at least an acknowledgment, even if it's after some reasonable time. I acknowledge all the messages I receive, and I expect others to do the same with me.