b4n requested changes on this pull request.
This is OK as an example of the behavior you want, but won't be merged like this.
We don't modify the Scintilla source itself, and Scintilla has all what is needed to change this from Geany's code. Also, we most probably won't force this one all users, so we'll want a setting somewhere (which one should be the default is more questionable though).
So as far as a review goes, please add a setting and set this option from Geany's code (somewhere in *editor.c*).