Well it turned out that the problem was more complex than just removing some special characters.
To make it short, when my sublime-completions file is short it works as expected, even with special characters. But when the file is long, anything but letters makes auto complete ignore words buffer from current file. I already tried using tabs with /t but it didn't work. Word buffer was ignored... I will try again, maybe I was doing something wrong as I'm auto generating the sublime-completion file.
So in my AS3 sublime-completions I have like 4 "addchild" triggers, and because I can't add special characters to the trigger nor a description to the snippet, I don't know which snippet I will trigger...
I filled a bug report here
http://sublimetext.userecho.com/topic/1 ... rd-buffer/I filled a feature request to add descriptions to snippets in sublime-completions
http://sublimetext.userecho.com/topic/1 ... -triggers/I hope someone (Jon Skinner) will notice this and make something about it... although it seems there aren't many people complaining about it.
I know nothing about Python, but I will take a look at your idea. Thanks.