Each game fork has its own rules. Additional forks may be possible if the particular game would allow it at the time. Reunifications must be legal in all affected forks.
Incidentally, the Babelfish translator does a reasonable job of the two German-language moves (although it's foxed on more than one occasion by my rather dubious grammar and spelling).
I think any move at all falls in the no-man's land between impressive and utterly insane. I shall look impressed while backing away slowly and making no sudden hand movements.