I have read some titan archive reports in the past as well and from all I can tell the problem is always with intention and thought behind it. I think it's public knowledge that Nivemus has long intended to split and I would assume that the new realm will have some form of independency as well?
Swordfell/Sol was punished because the entire idea (as explained in their letter by the titans) was to get strategic advantage. In the case of Nivemus I do not believe that is the case and I'm quite certain there should be no problem if there's at least a decent RP story behind it (which you should have, especially with the OI Duke history of Nivemus etc).
You can always ask some of the devs if you are worried and briefly explain the situation and thought behind it. Then you know for sure.
