How to report suicidal comments on YouTube?

Suicide and self-harm

Content that promotes self-harm or intention.
Users are not allowed to scandalize or dislike on YouTube. We allow users
to post content discussing their experiences with depression, auto
damage, or other mental health problems.

What to do if you see this content

If you find content in which
someone expresses suicidal thoughts or is hurting himself,
please contact the local authorities and mark the video to bring it to our
Inmediate attention. We approach these individuals with resources,
and work with suicide prevention agencies to provide assistance when
possible.

https://support.google.com/youtube/answer/2802245?hl=en