Hello, to find official information I decided to go to the source via website customer support ticket in Feb 2021: At the moment the company's stance is to grudgingly not do anything about it as it is very difficult to detect on a technical level. So currently it is a kind of "we look the other way, but we reserve the right to punish everyone using it without further warning" kind of situation. You could report them the same way as botters. If you need more information about this report function look at the website's FAQ section I cannot tell you the exact details but disconnects are still a challenge to figure out. As already mentioned we reserve the right to punish everyone without further warning."
Old information I was able to find that apparently is outdated: CM Reply (2015) "No player would be punished for simply quitting his internet connection. There is no way for us to know with 100% certainty whether this happened on purpose or if the connection was lost accidentally. The smart-exit function in tunnel services does the same. It cuts off the connection. There is no difference. For that reason, it is tolerated."