Yes, you’re onto something there RobberFly. Apparently I didn’t process all of the information when I made that last comment. I asked around about your specific example, and was told that there is another defining attribute besides Mks that can be shared among weapons. As you’ve mentioned, those Headhunter Autoguns were able to share blessings, and that part of the name is a defining part of their behavior and attributes. The takeaway from this is that there is another key statement in that section of the patch notes, but it’s not immediately apparent if you aren’t familiar with the term.
Each weapon pattern has unique Blessings available to them, and you can only swap these with Blessings belonging to the same pattern.
“Headhunter Autogun” in this case would be a pattern. What exactly are patterns? Well, that in particular is one of the main things we need to work on properly conveying within the game. I’m not confident I can adequately explain it myself, nor am I sure on how much I’m allowed to say, but I definitely don’t wish to give out incorrect information. One trick I was told you can use to determine which blessings are compatible is to look at your weapon skins. If two weapons can share a skin, they likely can share blessings as well.