Some apps send notifications that I can reply to; and some do not. I understand that this caused by the 3rd party app itself.
In my case, I use MeshCore a lot, and incoming messages notify to my Pebble just fine, like you’d expect; but I can’t reply to them. The MeshCore app is open source though, and if I knew what to ask for I’m sure I could find a way to get it updated …
So, can someone point me in the right direction to work out what to ask for at their end? 
-jim