You can do this, and historically some browsers did, it's called AIA chasing (which is why AIA is mentioned briefly in the blog post) The problem with AIA chas

You can do this, and historically some browsers did, it's called AIA chasing (which is why AIA is mentioned briefly in the blog post) The problem with AIA chasing is that it's a privacy violation. Not a huge one but enough to be completely unacceptable for say Mozilla. In fetching the needed intermediates we reveal which intermediates we needed, if you're Let's Encrypt you operate only a few intermediates and you issue a truly astounding number of certificates from each so that's barely information, but if you're a small CA and you have say a dozen intermediates you absolutely could arrange for say pro-Party A sites to all use intermediate #6 while also pro-Party B sites used intermediate #8 and then use the resulting data from AIA chasing to measure who is going to "Party A" sites and direct political advertising at those people...