The news feed isn't a reliable source to determine ALL who sent you responses as it changes continuously, even within a couple seconds. It's for the same reason the names come and go disappearing due to continous changes. Apart from your wall, IF your nbr posted.. there's no other way to know who answered if not by the feeble newsfeed.
To figure out who are your active nbrs.. you have to visit each kingdom by kingdom!
- posting walls if playing and noting if they answer
- looking for evident signs of life.. that's the various crafting buildings in movement
- additions of recent new event buildings
- observing their walls, and that of poster if msgs have been answered recently
- observing if crops change
- observing monsters if they have been defeated
It's not an easy job to do without deleting someone who is still playing.. as the major part of players don't keep their heart-bar full so as to show they are 'alive' and collecting hearts. Many players don't have the physical time to visit their nbrs, due to the inconveniences of slow loading and maybe do only a sample or only answer posts.
Judging if they have hearts showing is not reliable either as these could have already been collected and also for the fact that the game itself generates new hearts each day on all kingdoms even if abandoned.
I for example have over 400+ nbrs. What I do is to keep in mind who posts, dear nbrs we know for sure are playing and forum posters I know. Requests I send only to these without bothering about the rest of the list. It would take an eternity to clean out and I would hate deleting someone who might be in need, just away on vacation, or temporarily absent for RL problems. This allows me to add freely whoever calls for a 'help me' to as to see their kingdom and help out newbies when necessary.
My request list of nbrs I keep in my mind.. so when scrolling through the nbrlist.. send only to them. I usually send out double the amount, and only once! to be sure on the income and have no problems accumulating responses within an hour.
If we continue to send out groups of requests.. these overwrite our former requests.. making the delivery system start all over again leaving us without immediate responses, as remember, only 20 are delivered in a day. The others will be waiting in line for the next day.
Hope this helps.. even if a long reply