Addendum to that post: Michael Gerson puts the point pretty well here:
[T]his is a cover, if not a con. By the nature of health insurance, premiums are not devoted to specific procedures; they support insurance plans. It matters nothing in practice if a premium dollar comes from government or the individual -- both enable the same coverage. If the federal government directly funds an insurance plan that includes elective abortion, it cannot claim it is not paying for elective abortions.
And as NRLC points out here, the government will be collecting and funneling even the "private" premiums to the "private" insurance plans. This fits with my impression of the bill here, according to which it would be the federal government who made the contracts with "health care exchange" insurance plans. So the money is passing through the government's hands anyway, making the distinction between "premiums" and "subsidies" even more artificial.
I've also just updated the W4 post to include some additional information about the "public option" and abortion coverage. Update is at the end of the post.
HT Keith Pavlischek for link to Gerson article