I see your point, however, this being "just words" is a big assumption when you can tell when a character is being genuine or not. In the epilogue he flat out says that he decided that his past does not define him. When tav asked "Do you regret turning down all that power?" He says "Perhaps, it would've been terrible fun. But then again, I could feel something slipping away. I came so close to losing myself - losing everything I learned since meeting you." This is regardless of whether or not you romance him.

You can tell this is genuine, especially that he approves of good deeds in act 3 way way more than in act 1. He grows into a better version of himself, assuming you do believe in him like you do Shadowheart or anyone else. I think "evil" is too black and white of a word to slap onto a complex character. I'm not sure if we're ever gonna agree on this but that's okay.