The bookmarklet code is generated in JS and an Ajax call is made to compress it. When the Ajax call returns, the newly-generated bookmarklet code runs immediately, popping up a window with the node add form. This shouldn't be happening.

This might be solved by #1912830: Convert js code to php, since the Drupal Ajax handling will bottle encapsulate the generated JS, which will (hopefully) ensure that it doesn't run when it should not.