I mean full respect when I say this- but if you advocate for a law or policy, don't shy away from the hard questions about it. Think them through BEFORE you advocate for the policy, as part of your thought process of whether that's a good policy or not.

In this case, those hard questions are exactly why I'm NOT in favor of such a policy.

If you make it illegal to recommend suicide, you create a situation where anyone who says anything even vaguely pro-suicidal is open to both criminal prosecution and civil liability. So that guy who (without any desire to see the poster suicide) said take a long walk off a short pier now is facing criminal charges, will have a criminal record, may go to jail, and then he'll be sued by the family of the deceased and probably lose his life savings (or whatever he's not already spent on lawyers).
Or, what if it's not the disturbed guy from the scenario who suicides, but some other random person a month later and they see that the 'long walk off a short pier' post was in that person's browser history? Do we blame that person for every single person who suicides who might have read that thread?
That in turn has a chilling effect on any online discourse and you'll get a lot more people using proxies and VPNs and anonymizer systems just for basic online discussion lest something they say be taken badly and the same happen to them.

And then in the wake of some publicized suicide, some politician will say it's time to clean up the Internet to keep our kids safe, and they'll task an investigative agency with proactively seeking out such things. Suddenly online message boards are crawling with cops, and if you say anything even vaguely pro-suicidal your info gets subpoena'd from the platform and you get cops knocking on your door with a court summons.

Is this 'better'? I don't think it is.

To be clear-- I have great value for the sanctity of human life. I don't want to see anyone dead, including from suicide. I think encouraging anyone to suicide is abhorrent and inhuman and I would personally remove such posts and/or ban such users from any platform I moderate.
But that's my personal standards, and I don't think it right or practical to throw people in jail or ruin their lives because they don't agree.

I also think one part of free speech is if someone else wants to create a toxic cesspool community, I don't have the right to order them not to. I'm okay with requiring a warning label on such a space though.