Whenever someone reports a bug to me, I ask them if they use any site-modifying extensions. If they do, I ignore them completely, even if they wrote a long, detailed report.
Web authors make websites for standard web browsers. I do not consider a browser with site-modifying extensions to be a standard web browser, and it is not my job to test my website with all 1,000,000 extensions that exist on earth.
It all started six years ago, when my website contained <div id="ad" ... and somebody reported, that their adblock removes that element, but it is not the ad. What kind of a mental process should a brain perform to conclude, that it is a bug in a website, and not in their extension, which is supposed to remove ads.