Currently I’m in favor of this fast line art idea – but I’m saying “currently”, because this is a discussion and in discussions we listen to the other person and possibly change our mind if their arguments are convincing. Right? 
Some of the accusations and sentiment in this thread is baffling, considering the contents of the original post that went to great lengths to explain how this is not an “evil AI”. I think it’s worth remembering too that the Krita team were always careful with their messaging around AI/ML. They never said they will not implement any form of AI-assisted tooling. It was always about the ethics of that solution (i.e. not based on stolen work).
Maybe it’s a case of “we can’t have nice things”, because everything will be twisted and misunderstood, and even developing a feature in good faith will have a strong backlash that will outweigh the positives.
Perhaps it would be more productive if we bring up concerns and address them one by one?
For example, the data set concern – it will be donated by the users in good faith and with the respect of copyright. I can’t imagine anyone maliciously sending tainted data, but if that happens, the data set will be small enough that it will be feasible to remove the bad inputs and retrain the model. I also believe the data will be heavily scrutinized by the developers to avoid this very problem.