Are italics on the web bad for accessibility?

On a current web project, we've received word from the client that we can no longer have any italicized text on the website we are building.

When I asked for some reasoning, I was told that "our accessibility person says it's bad for accessibility", with no other justification.

Honestly, I've never heard of this before, so I tried to do a bit of research on it.

All I've been able to find is this post from 2007 which literally comes to the conclusion of:

I never found the text of any study that proves it. There's reference to one, and that's good enough for me. Instead, I am relying on the "everyone says it" method

With most of the post's references having long since rotted away.

As far as I can tell, the main reason italics were ever an accessibility issue were low dpi screens making small oblique fonts unreadable.

But in this retina world, I find it hard to believe that's still a valid reason.

So, what are the reasons for italics being bad for accessibility, and are those reasons backed by any real studies?