It is quite possible that it was dropped for new members, or old members with very few posts. It most likely will reappear after a certain number of posts have been made.
It is still there for me. They have changed the way PM works over the last few months.
It's beginning to look like the PM mail icon was removed from new posters on purpose. That would stop the problem of a new forum member joining just to PM a certain person, and never posting anything.
I think that the original way chosen to block messages to Comcast personnel caused unexpected problems for controlling PMs. Just an educated guess on my part.