Saying you'd exchange a body part that you can technically live without for something is a pretty common metaphor to the point where I'd say it's not glorifying self harm.
Its funny, because if you report obvious self harm or violence content in Spanish Twitter does nothing (like vaccines don't work, inject chlorine yourself, kill the president, organize a coup).
(Edited: typos)
I'm sorry that happens on Spanish Twitter, that's really unfortunate and it sounds like not a fun place to discuss things.