Interesting. Bitfinex changed their announcement now, this is what it says about those certain ERC20 tokens now:

"Restrictions on U.S. Persons Trading Certain Digital Tokens

Bitfinex will be barring U.S. customers from trading ERC20 tokens issued through "ICOs." That ban will go into effect at noon UTC on Wednesday, August 16, 2017. No trading of these tokens will be allowed for U.S. customers as of that date and time. Please note that nothing in this announcement should be taken as fact or opinion that any such ERC20 tokens are a security pursuant to U.S. law or require regulation under U.S. law."

Even though earlier they wrote, in the same announcement:

"Pursuant to the recent report of investigation issued by the U.S. Securities and Exchange Commission, Bitfinex is taking the proactive step of barring U.S. customers from trading certain digital tokens that may be deemed securities in the eyes of the SEC."

https://www.bitfinex.com/posts/216
https://www.bitfinex.com/posts/217

Having that announcement in the first place was unnerving. Having them change it without a changelog shows me they are really not to be trusted.