Blotting out Haman's name only some of the time?
At megillah readings, I'm used to people making noise to blot out every mention of Haman's name. Tonight I was at a Chabad reading and they had a different custom: they blotted out the mentions that used his full name or referred to his role (I guess the "important" ones?) but didn't blot out every single mention. They were marked in the copies they gave out for people to follow along in. (There was a little grogger icon beside his name in those places.)
I looked for footnotes in the book before handing it back in, but didn't see an explanation of the custom. It didn't seem like a good time to distract the rabbi with questions.
Where does this custom come from? Is blotting out all of them custom (and customs vary), or is this a point on which halachic sources disagree?