You are answering my every post! 
You got me thinking that I simply could add a new link and remove the My Posts one. But, I don’t feel comfortable removing the My Posts one: what would happen to the relationship it has with the js.sidebar.sections.community.links.my_posts.content parameter? What if I want it back, would creating it again exactly as it was be sufficient to re-establish this relationship?
So I would say it’s at least a UX problem insofar as the UI is misleading…? Also that would be great to make custom entries translatable, that would make sense if Discourse aims at making possible for every user to have its interface in their preferred language. But I might be asking too much.