So, there is a Clan in Fontan and Aurvandil.
That is set in stone. And the problem (seeing that I understand correctly) it is not that there is a clan, but to define if the way they formed the clan is bad for the game or not.
The way I see it is this: When you play with friends the OOG messages will happen. Friends will talk, it is easier, or quickier, to plan somethings with OOG messages on messenger or IRC than wait messages. And this will happen, and can disturb and exclude players.
I was in Averoth for a while, and I had different opinions from the ruler and other realm mates on what to do, and since I "know" him(don't live in the same country but we played together and have/had OOG contact) we even discussed things OOG.
Yes, it was hard to be part of the "gang" and in the end I ended up joining Astrum in the end. There was no big warm welcome, but everything(at least most of it I believe) was kept IC.
Now in a Democracy I find it easier to rebel against a clan. If a member is wining election running alone and with only a minority of votes that the other players have the ability to run as well and try to make other players vote for them.
If the clan doesn't exclude anyone this is possible and it won't be a problem to anyone and they'll find a way to continue playing or leading their ideas.
If this doesn't help them they need to be punished.
On the mass immigration to a realm, I see no problem to that, when you play in a realm and you have fun with the people of that realm, and then your realm is destroyed, i see no problem with you joining a new realm with your realm mates and trying to participate together, specially if they are active. They will participate, they will try to be part of the new realm. And it won't be a clan or anything illegal.