This is precisely the perpetual Catholic slander that Christopher Hitchens referred to regularly. A lie told by believers about several prominent freethinkers.
It goes both ways. On the one hand the religious want to claim eveyone as one of their own, especially in death-bed conversions. On the other hand, there are the rabidly anti-Catholic types who make up lies about people having been abused without evidence, as we see in this thread. Or the atheists who conveniently forget that quite a lot of "free thinkers" were religious.
Wittgenstein was not a Catholic because he had no faith, but he was respecful of Catholicism, had many Catholic friends, and asked for a priest to be present as he died. There's no evidence he formally converted.
What of it? What would Wittgenstein say to the syllogism, 'Some Catholic priests are child abusers, Wittgenstein was a Catholic in childhood, therefore Wittgenstein was abused by a priest'?
The only sources for the claim are evangelic Christian websites, and this specific thread. This thread is actually one of the top results for the search now. I've spent a lot of time reading Wittgenstein, and reading about Wittgenstein. This was never mentioned in any credible source I've come across.
Well, as mentioned in the article, at the time of writing the Tractatus, Wittgenstein was deeply moved by the kind of spirituality found in Leo Tolstoy's work. However, it's the explicit purpose of the Tractatus to draw a demarcation line between propositions of logic (and by this, meaningful sentences of philosophy) and any mystical or spiritual feelings, thoughts, or faith. So it really doesn't matter at all.
Wittgenstein was not a Catholic because he had no faith, but he was respecful of Catholicism, had many Catholic friends, and asked for a priest to be present as he died. There's no evidence he formally converted.