Force enable cramming (280 character tweets) on Twitter. NOTE: Stops working when you switch pages, refresh to fix. https://twitter.com/Prof9/status/912859110776950784

Twitter Cramming.user.js

// ==UserScript==
// @name Twitter Cramming
// @description Force enable cramming (280 character tweets) on Twitter
// @author Prof. 9
// @version 0.1
// @match https://twitter.com/*
// @run-at document-idle
// @namespace prof9.twittercramming
// ==/UserScript==

var initDataInput = document.getElementById('init-data');
var initData = JSON.parse(initDataInput.value);
initData.deciders.cramming_feature_enabled = true;
initData.deciders.cramming_ui_enabled = true;
initDataInput.value = JSON.stringify(initData);

// for CJK and etc
function getTwitterTextOptions() {
    var tweetForm = document.querySelector('form.tweet-form');
    var keys = Object.keys(tweetForm);
    for(var i = 0 ; i < keys.length ; i++) {
        if(keys[i].startsWith('jQuery')) {
            var jqc = tweetForm[keys[i]];
            return jqc.events.uiTextChanged[0].handler.context.attr.twitterTextOptions;
        }
    }
    return null;
}

function modifyTextWeight() {
    var opt = getTwitterTextOptions();
    //alert(JSON.stringify(opt));
    if(opt) {
        opt.ranges[1].weight = 100;
        opt.default_weight = 100;
        return true;
    }
    return false;
}

document.onreadystatechange = function() {
    function check() {
        var success = modifyTextWeight();
        if(!success) {
            setTimeout(check, 100);
        }
    }
    check();
};