he means that there is a code that resets all those checkboxes to default state of unchecked
this javascript will run and automatically do initialization whenever users open or reload the site
it's a standard practice of script writing to initialize/reset all inputs to default values onload
so the code exists for all users, not only for you...
This is correct. As it is Javascript that executes locally you can read the source so if there had ever been anything in it that caused the boxes to be checked you would be able to produce a copy of that code and prove it. The gormless troll thinks that just be repeating his false accusation over and over ad-infinitum it somehow becomes true.