Yeah it seems to be based on sympathy and causes messages when there is a mismatch between sympathy towards a realm and your diplomacy. So on Dwilight, Solaria gets messages like this one:
The local population strongly objects to the war on Pian en Luries.
In Fronen we get messages like these:
The locals do not understand how you can be allied with Melhed.
There are loud protests against your alliance with Thalmarkin.
