e-tags should contain markers. "reply" or "root". The event I first saw an issue with, had claimed to be in reply to the OP, while a secondary e-tag referenced my event. So some clients rightfully assume it is a reply to OP as it's explicitly marking it as such a "reply" while others appear to ignore this "reply" "root" marking and follow your assumption. To my surprise, Astral agrees with Amethyst. I do not know blebstr.