A little clarity for those who have never tested eXch.

Even though you can ostensibly choose "BTC-BTC", you will not be able to make an exchange. Perhaps sometime in the future the eXch team will rework the anatomy of the drop-down list so that the "Exchange rate not found for BTC / BTC" notification is instantly displayed when you select "BTC-BTC". But to be honest, this is not so important since you will receive this notification as soon as you try to enter your Bitcoin address or click the “Exchange/Сalculate” button