[O] how to best make characters invisible in a org-derived mode

[Christian Wittern]

Hi orgers,

In a mode derived from org-mode, I would like to hide some characters with a 
special function to make the display cleaner. There are two cases:
 - special characters that should be always invisible
 - strings matched by a regex that should be invisible

I would be glad for any pointers or ideas on how to implement this, either 
by piggy-packing on org-mode code or by using generic Emacs features.

All the best,

Christian

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Christian Wittern, Kyoto