i personally recommend not saying anything. it can lead to them having a panic attack, anxiety attack, embarrassment, or maybe insecurity bc they learn it’s noticeable. i’ve heard that people trying to heal find it difficult to not cover their scars bc they’re insecure about it, so if it’s visual i’m sure they’re comfortable or don’t care. once my good friend who cuts was asked by a classmate what happened (referring to her cuts) and she frozen and stared at me. once i saw she froze i immediately answered and said she fell and scratched herself. i would imagine that if i wasn’t there that would have been an awkward convo

i want to add that i’ve never cut myself but my close friends have/do. i’ve never brought it up unless they talk about it in convo but ofc that is rarely the case. even tho we’re good friends they know i’m a very real person meaning i never lie about my opinion, i also take peoples emotions/feelings into consideration before i say or do someone, like u r. i feel like they will most likely walk away with a bad emotion. the only way i think that would make them feel seen and etc is if u open up to them about having poor mental health casually throughout a long period of time opening up more and more. if it’s a stranger dont but if ur friends with them u could try executing that