Org-export fails with guillemets

I use org-mode to write novels and short stories, but I have a problem with exporting. When I use the emphasis near a guillemets, such as `and the he said: «/That/ is not a banana` In this case, the begin of the emphasis is after the word “that”, not at its begin. I remember I was able to fix it a while ago adding guillemets on a configuration string, but I forgot its name and location. Thank you

You can insert a zero-width space in front of the first / See https://orgmode.org/manual/Escape-Character.html#Escape-Character

Possible, but not really a solution: it forces me to concentrate on presentation rather than content, like XML/HTML. It should be a string in org that defines separator: my need is to know how to set it

There is also `org-emphasize` to do the necessary work for you automatically. As for alternative separator, it is a no-go unfortunately. External packages often rely on standard separators.