When was the last time you double texted someone?
Even if it was recently, it probably wasn't something you were ecstatic about.
According to Anita Chlipala, “double-texting can make someone come across as intense, desperate, impatient, or anxious”, depending on the frequency of double-texting. While double-texting certainly isn’t a bad thing, it is something most people feel uncomfortable doing.

A possible solution to this could be the addition of a “Nudge” feature, which would allow you to “nudge” your friend, sending them a notification to respond to your message. There would probably be certain considerations to implement this feature such as how many times you can nudge a person and how long after you send your message could you nudge them. Either way, gently reminding your friend through this feature definitely trumps double-texting in my books.