You can report any post or comment on reddit, an one option is "self-harm or suicide" https://i.imgur.com/aGLtTeW.png I think it meant in a way that you are afraid of the person. If you are the one reported then you also get an automatic system message from reddit: someone thought you might have problems etc. Basically the suicide alert.

Anyways people use it all the time in every single sub for any unrelated thing, just because they hate you, downvoting is not enough, trolling etc. In sport subs it's very common to report opposing fans with this option for example