nyamatongwe is Neil Hodgson, the Scintilla developer. Just wait for his response.
So he's responded*, saying something about using the API to change the following settings: SCI_SETWORDCHARS, SCI_SETWHITESPACECHARS, SCI_WORDRIGHT and/or SCI_WORDRIGHTEND. Can this be configured in Geany somehow?
* http://tinyurl.com/5frmdf (https://sourceforge.net/tracker/index.php?func=detail&aid=2100400&gr... 2439&atid=102439)