Update: The Issue has been resolved.

Summit devs, could you just take a look on the issues before the next update?

I tried looking a little more into it, and so far as I can tell, Saymaz should not be able to see who performed the mod actions. You're right that them being a mod on lemmygrad should have no impact on their ability to see the mod name for a mod action on hexbear. Only admins and other mods for that comm should be able to see who performed the mod action. But it doesn't appear to be something having to do with the app Summit either, which does abide by the lemmy protocol for not sharing the names of mods on mod actions. Which is the default setting, though instance admins can choose to share that information if they want, but almost none do, and hexbear certainly doesn't. So I still really don't get why Saymaz was able to see that it was Alaskaball. It's weird.