Player-adequate

// ==UserScript==
// @name Player-adequate
// @namespace arhivach
// @include https://2ch.hk/*
// @include https://arhivach.org/*
// @include http://arhivach.org/*
// @author AHOHNMYC
// @version v0.0.3
// @grant none
// ==/UserScript==

function handlePlayer(){
  let m = {t:0, l:0};
  new MutationObserver( ()=>{
    let vid = document.getElementById('html5video');
    if (!vid) return;
    vid.addEventListener('mousedown', ({clientX: l, clientY: t})=>{ m.l=l; m.t=t; });
    vid.addEventListener('click', e => (m.l != e.clientX || m.t != e.clientY) && e.preventDefault());
  }).observe(document.getElementById('fullscreen-container'), {childList: true});
}

function handleHandler(){
  let mo = new MutationObserver( ()=>{
    if ( !document.getElementById('fullscreen-container') ) return;
    handlePlayer();
    mo.disconnect();
  });
  mo.observe(document.body, {childList: true});
}

if ( document.getElementById('fullscreen-container') ) {
  handlePlayer();
} else {
  handleHandler();
}