Here are some of the arguments from that topic (there are a few so they're in Spoiler tags):
http://i51.tinypic.com/b7gw3p.jpg
- ..."'Sotha Sil,' said a serious-looking Dunmer in a white cloak, shaking the Prince's hand and showing him to a seat."http://www.imperial-library.info/content/morrowind-2920-last-year-first-era
http://i51.tinypic.com/1pz56u.jpg
http://i51.tinypic.com/28a3km0.jpg
There were (as with all of my pics) taken from in-game and have been marked with the:
HELSETH SEAL OF QUALITY :thumbsup:
...
I have been reading 2920, Last Year of First Era and that is the ONLY reference to Sotha Sil having Dunmeri skin. But that series also states that Vivec is a tall Dunmer (not half-Dunmer and half-Chimer) and Almalexia has black hair (not red), so the debate hasn't finished.
My opinion is still that it would make sense for Lord Sotha Sil to be Dunmeri, but he doesn't look like it in-game and the only in-game reference can't be trusted.