I found this question: Add a little 'x' so users can close the new user contributor indicator. But it's about a specific user question.
This indicator only distracts attention from the question itself. So, would be great if we could hide/disable this indicator completely. For example, you can add such option on the profile settings page.
As a workaround just for now, script for Tampermonkey:
// ==UserScript==
// @name Contributor indicator cutter
// @namespace http://tampermonkey.net/
// @version 0.1
// @author Suvitruf
// @match *://*/questions/*
// @match *://*/review/*
// @grant none
// ==/UserScript==
(function() {
'use strict';
var doc = document;
var newNode = doc.createElement ('style');
newNode.textContent = '.new-contributor-indicator {display: none;}';
var targ = doc.getElementsByTagName ('head')[0] || doc.body || doc.documentElement;
targ.appendChild (newNode);
})();