It is the same question :) Thought I throw it out here to!
1. I have never ridden any other w650 but I think its running completely normal.
2. The plugs doesnt look oily, more chocolate/tan like, pretty normal I guess.
3. I cleaned the airfilters last summer, then the filters were pretty oily, and the airbox to. and the bike runs a lot better when I cleaned them and put on the "right" amount of oil on them. Doesnt know what the previous owner have did.
Thats waht I´m thinking also, but just as you say, it shouldnt leak anything there anyway?!
It seems that this oily, sticking thing has been there for a while. It is almost black (as you can see in 2 of the photos) and very sticky, it has not coming recently but this was the first time I checked under there.
I just DONT want it to be any blown head gasket!? :(