Hi Mark,
Yup, been there, done that. As soon as you grind that tab off, you find out what its purpose was. It keeps the blade from closing past the ball detent and bottoming on the spacer.
I didn't find it to be a big deal, but if the blade was squeezed closed all the way onto the spacer, it was even harder to get to the thumb disk.
The updated ones have all that sorted out though. No more need for that little thumb disk stop with the stop pin in the new models. Great little extreme use folder. Mine happens to have a very good liner lock that passes all the tests, so with the M-2 blade, I consider it quite the better of its peers like the Emerson. I think you have to go to a REKAT Pioneer to get a stronger small folder.
Harv