The sceptics point to the absence of any mention of a return to faith in Gramsci's final letters, and to the fact that he is buried in the Protestant cemetery in Rome, traditional resting-place of unbelievers (the graves of Keats and Shelley can also be found there) as counter-evidence. And, on the face of it, a reconciliation between the greatest Marxist theorist of the twentieth-century, and the faith that he spent his life seeking to replace, does seem rather unlikely.
On the other hand, I've often felt that there are parallels between Gramsci's revisionist Marxism and the more sacramental, incarnational forms of Christianity. Just as Catholic theology views humanity as fundamentally good, and (at least in theory) seeks to 'go with the grain' of human culture and society - so Gramsci's Marxist humanism attempts to identify the 'good sense' in everyday 'common sense', and to build on existing social structures. And Gramsci had a great respect for tradition, believing that the new social order would incorporate the best of the old (see these posts). By contrast, you could argue that there are distinct similarities between extreme Calvinist Protestantism, with its negative vision of humanity and profound suspicion of culture, and the slash-and-burn revolutionism of the Leninist far left. So, whether or not the deathbed conversion story turns out to be true, perhaps Antonio was more Catholic (in a broad sense) than he, or his more secular supporters, would likely to admit.
I must confess to not having read any Gramsci for years. But there was a period in my life when the Prison Notebooks were my main political and intellectual reference-point. It's enough, now, to open the tattered pages of my Lawrence and Wishart edition, for me to be transported back, Proust-like, to the heady days of the mid-1980s, and I'm standing again in the Centerprise Bookshop on Stoke Newington High Street, leafing through the latest issue of Marxism Today or Red Letters, the smell of vegetarian food wafting through from the cafe, my 'Coal not Dole' badge proudly displayed on my donkey-jacket. Ah, memories...
(Via Dolphinarium, now added to my blogroll)