I've never heard of Irish Moss negating the effects of oatmeal: Irish moss helps keep floculants coagulated and keeps your beer from tasting yeasty and looking cloudy. So if anything, I think Irish moss helps mantain the dry notes that oatmeal brings to a stout. Proteins aren't totally settled out: otherwise, Irish moss would be considered a step for eliminating chill haze...and the beer wouldn't be able to have a head.
On Tap: Barleywine, Coffee Oatmeal Imperial Stout (big big beer)
Fermenting: Double Simcoe IPA
On the Bench: Racer 5 IPA
"One of the first things early caveman did, when he crawled out of the mudd, was to make beer. And cavemen everywhere are still making beer...and drinking beer." - Jean Sheperd