User blog comment:Harold Burned-Mane/The Truth about Ulfric Stormcloak/@comment-13446185-20130916021214

Regarding your theory of Igmund being a Thalmor asset:

I'm pretty sure if you meet Igmund in the Thalmor Embassy he tells you that he doesn't trust the Thalmor. I think the reason why Ondolemar is in Markarth is because of the whole "Markarth Incident" stuff.