What Lady Nerevar said, basically. The 36 sermons of vivec are filled with stuff concerning chim, anyone in-game with a mind other than a tribunal-obsessed preacher could potentially find these clues that Vehk laid throughout the volumes and come up with a conclusion of his/her own. While it wouldnt be the easiest thing to comprehend for a character in the game, its a possibility.
On a side note, I dont suppose its possible to contact MK himself? I know its a bit much to hope for (besides his special occasion posts) but still, i have one or two questions about Sotha Sil
He has quite a few accounts here at the forum, IIRC. The 'Merry Eyesore Elk' is one I believe. I'm pretty sure Lady Nerevar has a line to him though. But it is probably easier to just ask everyone else here in the forums
It actually took me a while to realize that the Omega MK poster isn't MK,
I'm not sure what his username refers to though, besides MK.