Both parts are great. I learned quite a few things myself despite having worked with blueprints for a long time.
Seems very reasonable. The whole idea of having both an interface and a boolean was a bit much, I agree. This is clean and should work fine. If sometime in the future you have many different kinds of units with different counter attack behavior, an interface would make sense, but if this is not the case yours is the cleaner solution.
I certainly did not remove them. Maybe YouTube incorrectly marked them as spam or something? I’ll take a look and see if I can identify what might have happened. Very annoying.
Edit: Nothing in my Held for Review or Likely Spam folders on YouTube. What specific videos are you not seeing your comments on? It will help me figure this out.
When you compile a parent blueprint, UE4 should automatically compile all child blueprints inhereting from it, which will mark them as having to be saved. You should not have to worry about anything breaking if you only compile and save the parent.