##Javascript with jQuery, 121 bytes

<!-- language: lang-js -->

    $.post("//codegolf.stackexchange.com/posts/84546/comments",{comment:12345678901‌​23456,fkey:localStorage.getItem`se:fkey`})

Thanks to Ismael Miguel for several bytes!

The `fkey` parameter is unique to your account, and can be found by examining local storage contents of your browser with a StackExchange page open. This code must be run in a browser with an open StackExchange session present. It automatically loads the `fkey` parameter from the browser's local storage (previous versions of this submission required it to be manually entered).

Unfortunately, the `ppcg.lol` URL can't be used, because it doesn't pass POST requests through.

Fun fact: if you attempt to run this code without the proper `fkey` value, you get an [HTTP 418](http://codegolf.stackexchange.com/q/41638/45941) response:

[![teapot][1]][1]

Example of how to find the `fkey` value in Chrome:

[![fkey][2]][2]

Apparently Winterbash stuff is still being stored. Neat.

For reference, the same thing in vanilla Javascript would be 333 bytes:

<!-- language: lang-js -->

    var http=new XMLHttpRequest()
    with(http){
    open("POST","http://codegolf.stackexchange.com/posts/84546/comments",1)
    setRequestHeader("Content-type","application/x-www-form-urlencoded")
    setRequestHeader("Content-length",62)
    setRequestHeader("Connection","close")
    send("comment=1234567890123456&fkey="+localStorage.getItem('se:fkey')}))}


  [1]: https://i.sstatic.net/rX32H.png
  [2]: https://i.sstatic.net/8lerc.png