Actually, NPCs can/do close Oblivion gates. There are at least three quests involving this.
I can't really comment on Radiant AI, but I will say this, it came to a point where the AI was, literally, ruining the game for the PC.
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Also: Picking mushrooms is an sacred Elder Scrolls pastime, just as killing rats is a general RPG tradition.
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You gain 1-5 experiance points for each mushroom?