It had the interesting effect of making me feel like a jerk for ever declaring war. When playing as pacifists I didn't want to declare war for RP reasons, and when playing as militarists I didn't want to declare war because everyone was a pacifist and didn't bother me.
Except the gestalt consciousness slug people down south, who kept sending me insults despite being inferior to me. I finally gave them what they asked for, and then groaned when they kept sending me insults despite me beating the snot out of them.
Oh, and the driven assimilators next to them. They were perfectly fine neighbors for about 200 years, at which point I finally accepted a war invitation to get rid of them because I got tired of empires asking me to help get rid of them. That turned into a real pain because I wasn't the primary aggressor and thus couldn't force a status quo, and I'd gotten all the war exhaustion out of them I could without capturing all of their planets. Capturing their planets was looking to be a major pain in the butt and half of them were filled with things other than robots which I didn't want to deal with once I took the planets.
When I did finally capture two of their worlds, I couldn't even figure out how to displace the weird aliens left behind. Does there have to be space open in an empire accepting refugees for them to actually be displaced? I ended up figuring out how to release them as vassals, so that solved the problem at least.
Anyway, the war in heaven triggered and alliances changed enough to force the war to end. Lesson learned: just like I'll never join another federation, I'll never accept another war invitation.
Then after the Contingency nearly wiped the driven assimilators out, they started sending insults to me...