Argumentum ad Jimbonem is the logical fallacy that "what Jimbo said" is The Truth™. Avoid creating policy proposals based upon vague (or even precise) interpretations of his words.

Nobody likes to be misquoted, and Jimbo is no exception to that.

Misquotes can originate by ignoring the original context of a quote: so if you're thinking about quoting someone in a talk page discussion, the very least you should do is to look up the original context of the quote to check whether it really applies: you'll see that often it is not possible to use the quote for what you intended. If you're adding or removing emphasis, or applying an ellipsis, or whatever editing of the quote, be careful not to make the quote into a contorted travesty, and always clearly indicate when and where the layout modifications were applied.

For this reason it is usually unacceptable to present something in a quote-like format without clearly indicating where you got the material for the quote. Preferably also add a hyperlink to where you got it, to make it easier for others to check whether the quote really occurred, and was not quoted out of context.

The reason why so many argumenta ad Jimbonem cause grief is that they are more often than not misquotes to begin with:

[Unsuspecting Wikipedian:] I thought that I had heard that you were [...]

[Jimbo's reply:] Good grief. I know this will sound harsh, but I think you should perhaps consider finding another hobby if you think "I thought I heard that..." is a valid basis for inclusion of a claim in an encyclopedia!--Jimbo Wales [...]^[1]

• Benevolent dictator article at meta: "It should be noted that Jimbo disputes [the benevolent dictator] term."
• Founding principles, which since March 2007 no longer says "Jimbo Wales as ultimate authority on any matter"
• Wikipedia:What Would Jimbo Do?
• Wikipedia:Appeals to Jimbo
• m:The Wrong Version#Involving Jimbo