Scenario: Assuming I (CH-based, non-US national) buy crypto assets on one of the big US-based platforms (Kraken, Coinbase, etc.) and I do not move these assets to a wallet but leave them in the account on the platform.
Question: As far as I am aware the US levies taxes both on crypto holdings (wealth) as well as on capital gains. Would my holding and/or selling (with profit) of crypto on a US-based platform create any tax obligations in the US?
No takers? 
Background are reports that the IRS will receive information about all accounts with crypto trading above a certain threshold:
All I could find are guides for US tax payers, for example on Coinbase (https://www.coinbase.com/de/learn/tips-and-tutorials/crypto-and-bitcoin-taxes-US).
The Terms and Conditions, f.e. at Kraken, only state that “It is your responsibility to determine what, if any, taxes apply to the trades you complete via the Services, and it is your responsibility to report and remit the correct tax to the appropriate tax authority.”
Generally there shouldn’t be any tax implication if you’re not considered a US person. In the US it’s typically taxed as property so only capital gain tax. Might not even need a W8-BEN since there’s nothing to withhold.