A lot of arguing apparently.
There are many factions (the word replacing tribes, I think) in Ireland, arguing over all sorts of things, and frankly, for a tourist, it gets confusing: Unionists, Irish Nationalists, Republicans, Catholics, Protestants, Loyalists, Separatists, and so on.
But back to the signs: those signs pointing to Londonderry/Derry from the Republic of Ireland might say just Derry, and those in Northern Ireland might well read Londonderry, until vandals arrive with spray paint. It's easy to paint out London, but harder to add London to signs just reading Derry, and we didn't see any of those.
We stayed in Londonderry/Derry, the only remaining completely walled city in Ireland, in a B and B right across from the wall built in the 17th century.
This was the view from our room:
This is the gate at the corner of the street we stayed on. Unlike the gates in Belfast, the seven gates through the wall are open all of the time.
But the open gates don't mean that the disagreements are over. This sign was in the parking lot on the other side of the wall.
From what I could piece together of the various bits of history we learned, I have come to the conclusion that if the Irish weren't fighting off invaders, they were fighting amongst themselves.
They should stoppit! and enjoy the beautiful, fascinating country they live in. Or, that is, countries. Northern and Republic of.