Exactly what I needed to know. Much obliged.
When you remove the plungers, you may break the little hooks located at the top of the plungers. Some or all of them.
There is one little hook on the top of the plunger (where the keycap goes).
When disassembling a Realforce or a Leopold FC660C, it's unavoidable, you break most of them. I'm not sure about the HHKB, but my bet would be that it will be the same.
It's inconsequential. A small part of the hook will be removed, but the hook has very little function. It helps holding the plunger in place when you put back the top plate in place when you hold it over the PCB. From experience, even when the hooks have been damaged the plunger still stay in place and you can easily reassemble the keyboard.
Once the keyboard is reassembled, the hooks have absolutely no function.
The only thing I recommend is that you remove the plungers on top of a sheet of paper, so you can get rid of all the small bits of plastic that will come out (the tips of the hooks). No small bit of plastic should remain when you reassemble the keyboard.