L'Osservatore Romano, the "semi-official" newspaper of the Vatican, claims that scientists who objected to the Pope's planned inaugural speech at La Sapienza University relied on out-of-context information from the Italian Wikipedia's Pope Benedict XVI article in arguing their case against the Pope. A petition against the visit was signed by 67 scientists, sparking student protests and leading to the cancellation of the speech.
The scientists' letter quoted then-Cardinal Joseph Ratzinger in a 1990 speech as agreeing with philosopher of science Paul Feyerabend that the Church's conviction of Galileo, for teaching heliocentrism, was 'rational and just'. In a speech given several times in late 1989 and early 1990, including once at La Sapienza University, Cardinal Ratzinger discussed the Galileo affair. According to an English translation of the published version of the speech, Ratzinger used recent views on the topic as "a symptomatic case that permits us to see how deep the self-doubt of the modern age, of science and technology goes today."
According to an English-language report of its story, L'Osservatore Romano suggests that "whoever took the quote from Feyerabend could not have read the rest of the entry in Wikipedia, as he would have realized that the meaning of Ratzinger’s statement is exactly the opposite of what the 67 claimed the Pope was saying", and "that no man of science would use [Wikipedia] as an exclusive source for his research, unless he checked the veracity of the content."
The account of Ratzinger's speech in the petition letter nearly matches a part of that given in the Wikipedia article in versions from the time of the petition's origin, around January 13. (The wordings differ by a single tense change.) The quotation in Wikipedia, which differed slightly from the text in the cited published version of the speech (this difference was not noted by L'Osservatore Romano), was followed by a claim that '[Ratzinger] agreed with [Feyerabend's] thesis that Galileo had maintained as true a theory which was subsequently corrected by modern astronomy'. The cited published version of the speech does not substantiate this claim, and it was not included in the scientists' petition. The petition did say, however, that its signatories had been offended and humiliated by Ratzinger's supposed endorsement of Feyerabend's words.
L'Osservatore Romano dates the La Sapienza speech to March 15, 1990, the same date on which the Wikipedia article and the scientists' petition say it was delivered in Parma. However, Ratzinger's 1992 book, Svolta per l'Europa?, cited in the Wikipedia article, says it was delivered at La Sapienza (in Rome) on February 15 of that year. It is apparently the common discrepancy in the reported location of the speech which led L'Osservatore Romano to suspect that the scientists had relied on Wikipedia.
L'Osservatore Romano's accusation that the quotation in the scientists' petition was taken out of context also seems to be based on a later version of the Wikipedia article, which had been altered considerably by a series of changes on January 15th. However, the petition had already been written before that date, and did accurately reflect the state of the Wikipedia article as it stood at the time when the petition was written.
The earlier Wikipedia account, including the quote, may have been derived from others, such as one on the Tradition in Action website, where similar claims are made about a March 15, 1990 speech in Parma, with citations to articles in Corriere della Sera and 30 Dias; whether Tradition in Action accurately reflects those articles is unknown at this time—Tradition in Action or the articles it cites, rather than Wikipedia, plausibly could have been the source the scientists used. Ratzinger did in fact repeat the speech several times in different cities about this time, and it is possible that the slight difference in the wordings of the quote might reflect a different deliverance of the speech.
Paul Feyerabend's autobiography states that Ratzinger gave a speech on this topic in Parma in 1990, but does not specify the date.