The study claims that Bitfinex’s secondary virtual currency, Tether, was used to buy other cryptocurrencies to achieve this. They suggest that half of the increase in Bitcoin’s price in 2017 is traceable to Tether being deposited in exchanges, prior to a spike.
http://www.the-blockchain.com/2018/06/13/fraud-experts-study-links-tether-to-crypto-price-manipulation/
But isn’t it simply the case that when Tether holders see BTC price and volume rising on key exchanges, that they would obviously use their Tether to buy BTC on any other exchange where the price hasn’t reflected that move? Essentially just an arbitrage trade.
& that Tether holders would obviously buy BTC as soon as there’s great BTC news, that’s why they’re in Tether not fiat so that they’re able to take advantage of clear BTC price moves quickly.
So obviously there is a huge move from Tether first into BTC on major positive news or technical indicators, but they are not causing the spike, just doing so first because the money moving from fiat to BTC on good news/other takes longer to get into BTC.