“Thank you for reverting to us”

I'd certainly never heard this before. Oxford Concise has nothing in the sense of reply, but funnily enough Oxford Advanced Learner's does - calling it Indian English and rather formal, giving the examples:

"Exellent openings—kindly revert with your updated CV."
"We request you to kindly revert back if you have any further requirements."

There's a bit about in this book, published in Singapore - "English as it is Broken 2' , where it calls it 'local usage'- http://books.google.pl/books?id=RmehtgPM1H8C&pg=PA94&dq=%22revert+to+us%22&hl=en&sa=X&ei=Jf2mVLLjD8XwUsCrgaAL&redir_esc=y#v=onepage&q=%22revert%20to%20us%22&f=false

Not everyone in India likes this use, though - http://www.newindianexpress.com/education/edex/Revert-Should-Not-Be-Used-to-Mean-Reply/2014/03/03/article2083266.ece

It certainly does seem rather stilted, and the addition of "back" makes it even worse.

I see it a lot here in the civil service in Bermuda - I think it started with ex-Regiment officers who ended up in the civil service and it spread and infected the the entire senior level of the service.