I read the Guinness discussion threads with interest and would like to add the following:
I was at the Guinness brewery a few months ago and to the best of my knowledge, they use nothing but a pure Saccharomyces culture. Fermentation no longer takes place in any wooden barrel and there is no Brettanomyces. Fermentation, in wood, would lead to inconsistencies in the final product profile. The "acridness" that some describe, would likely come from the roasted barley used in the process.
Guiness for the Irish market is not filtered, it is centrifuged. Guinness for Australia and New Zealand is filtered and does not use isinglass because of the legislation requiring them to label the cans as containing "fish products". Isinglass does not find its way into your pint glass, or can.
Guinness Extra Foreign Stout is not found in Dublin because it's FOREIGN. It was originally brewed to its higher ABV to survive the trip from Dublin to the warmer climates by boat, sort of like IPA. Incidentally, Guinness has about 40 IBU, which is up there in terms of bitterness, but somewhat cloaked under the roasted barley. I would be suspect of a rumour that Guinness Nigeria uses sorghum in their formulation. Have you ever had a sorghum beer? It's not quite what you think it is. The use of an adjunct such as grits or corn syrup is more likely and if the final product was pretty foul, you could be sure Guinness Ireland would do something about it.
As for the slanging match that went on about people with no taste and whiskey drinkers: There is no one beer for all occasions. Each one should be appreciated for it's unique characteristics, much like a bold red wine and a roast. Scotch has it's place too, and a single malt should be appreciated for it's unique character. Resorting to calling someone a whiskey drinker is poor form and has no place in a discussion.