I really do not see how taxing cryptocurrency at the exchange level or on the blockchain level (e.g., Steemit, Ethereum) is going to be done currently. The systems are not in place to make it easy for folks to be tax compliant so I envision a tremendous amount of non-compliance not because people don't want to be (although some surely don't) but because it's extremely difficult to calculate manually. You alluded to this point re: tax accountants.

I'm not aware of any US regulatory agency providing an easy solution to the exchange challenge. For fiat gateways like Coinbase and Gemini, this tax compliance should be easier because they are already regulated financial institutions so they should have the systems in place to assist their users.