Somewhat OT, but one thing I'd like to comment on is that a couple weeks ago, I removed a stubborn quill stem from an old school Marin MTB. It just didn't want to "act right" as I would remove it similar to what you've described above, but it just didn't want to come out. It took quite a lot of taping on the bolt to free it up, and only then was I able to remove it. Come to find out, the wedge on the end of the stem was made of aluminum! I've never seen that before. The wedge had corroded and welded itself to the inside of the steerer tube. I cleaned it out and greased everything up and it slid back in like butter. Weird though. That particular Marin model wasn't notable for being lightweight or particularly high-end, so why the effort to save weight on that particular component?