Well, Wikipedia stores previous versions of the article, and those can be restored. So if someone deletes something the next person can just add it back in. Which is basically what the discussion pages are for: arguing over whether or not something should be in there.
And, temps, using an encyclopaedia to provide a general introduction to something has always struck me as perfectly acceptable. Just so long as you don't assume that what it says is entirely accurate without checking elsewhere there really shouldn't be a problem
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