The underlying argument has little to do with Orwell and Self per se. It has more to do with deeper questions about the purpose of style.
Will Self is making the same point that many others have made in response to the idea that transparent prose is the ideal for criticism and narrative fiction. Orwell's
famous essay on style, which privileges Anglo-Saxon words over the Latinate variety in terms of vigor, is useful and even recommended by a number of writers I've known. Katherine Dunn, author of
Geek Love, has practically made a science out of how and when to introduce Latinate words.
The problem is that (i) pellucid prose itself can become mannered and inexpressive (see the innumerable Hemingway imitators of the '30s and '40s) and (ii) taken too literally, Orwell's stylistic preferences can be used by dogmatic critics, editors and readers to rule out the work of many, many gifted and fecund writers -- including that of Mr. Self, whose diction can be pleasantly quirky.
Self seems to be saying that every writer should not be expected to ascribe to Orwell's precepts for stylistic excellence; that stylistic opacity is not always a bad thing.
I tend to agree. As much as I respect the sapphire-glass clarity of Andre Dubus, I also love the elaborate chamber music of John Hawkes. And you can't have Flaubert without a bit of clarity
and opacity.