If I had read that, I would have adressed the issue long ago. Well, ^ban^ is aware of it now.
My character in Fissoa is both Ruler and Knight of Drowenton. Apparently that shouldn't be even possible, but it somehow worked out 
[Skyn was Lord of Drowenton, and Victorian his knight. When he was elected ruler, he appointed Victorian as the new Lord. Somehow, Skyn stayed under Drowenton in the hierarchy (but blacked out, like when someone new arrived in the realm. Not really an oath, but nonetheless linked to the region somehow). Victorian was somehow able to offer Skyn an oath. The allegiance window was kind of conflicting, though: "As knight of Drowenton, you owe your allegiance to Victorian." and "You are Grand Duke of Fissoa. As such, you owe your allegiance to nobody but yourself".]
This is a long standing and known issue. A ruler can't take a NEW oath, but they kept any oath they already had. When you step down or are removed from a Lordship position you become a "noble" of that region, which is why you are greyed out. You retain this status until appointed Lord of somewhere else, or you take an oath somewhere else, both of which should be impossible for you now as a ruler.
