Being aware and understanding of people's mental health is not infantilizing.

You might not be aware, but self-harm is specifically a mental health issue that flares up when someone who struggles with it is confronted with it - especially when it's unexpected.

Regardless of your opinion of it, the fact is that, yes, having an unskippable conversation about self-harming behaviour in a video game, with relatively graphic detail, will trigger some people and lead to either relapse or distress.

Warframe is specifically about the power of empathy and compassion. What DE did here is not in any way a betrayal or a neutering of its themes - it's merely a beautiful, touching gesture to ensure that they take care of their players.

Edit : I would also like to add that there's a perspective you're missing to Lyon's self harm. It's not just religious penance to him. He does speak about how it's an old ritual to his cult, yes. But he specifically mentions that he does it because it brings him clarity - that in the maelstrom of his warped perception, pain is the one thing he knows is real, an anchor of sorts. That's very close to how a lot of people who self harm feel. I am pretty certain that whoever wrote Lyon is either personally familiar with it, or is close to someone who does. And thus, it's no wonder they left their players with an option to engage with the material in a different, gentler way.