Al Kondo wrote:
I am in the process of putting wall covering (essentially wall paper)
on fiber board panel in my kitchen. This panel is made to look like
fake white 4" tile. My wife does not like it and we have decided to
cover it and paint it. I think it will work out except for one
thing. A few places on the fiber board has joints which shows after
covering. I tried to prevent this problem by bridging the very narrow
joints with some duct tape. However, it still shows. My thought
now is that I would use joint compound over the wallpaper where the
joints show through.
Thanks, Al Kondo

I've seen it done before, exactly as you described using joint compound.
Well, not the duct tape idea ;o)