Juan,
Apologies, I did not realize that the information I requested was already in the title of your post.
DevStyle is compatible only with Eclipse Neon and higher versions, which is why you’re seeing a crash with your Luna based IDE 🙁 I’m afraid there’s no way DevStyle will work with Luna, and you will have to uninstall it.
Our marketplace listing should not allow it to be installed for earlier versions – do let us know how you installed DevStyle. It looks like we’re missing some constraints in the plugin itself that should have prevented it from being installed into Luna, we’ll look into fixing that, sorry.