[nickff]

Something can be an indirect subsidy and a Pigouvian tax at the same time; they are non-exclusive options. I see the carbon tax as both, and am opposed to both.

There are no 'pure market[s]', and there never have been. The 'pure market' was a straw-man invented by anti-market people.

[jimmytidey]

It seems to me that subsidies and Pigouvian tax are exclusive if they are to mean anything. Perhaps I'm wrong?Can you point me at a discussion of this?

I think you are right that few people explicitly say that pure markets exist. But implicitly many people make arguments based on some kind of some unregulated state of nature, for example on this thread.