Exactly, these are my thoughts as well. I wrote on bitcoin.de support and they replied me in few hours that they do not see any price manipulation and using a bot is not illegal.
Yeap. I think it's currently legal due to bitcoin or cryptocurrencies in general being currently unregulated. Bots are being widely used among multiple exchanges, even with the top ones like Bitfinex and Binance. As with manipulation? I'm not sure. I think price manipulation isn't legal nor illegal; in the cryptocurrency space at least.