I just found another non-working shortcut : []+tab doesn't change anything in math mode ; here i don't even need to be between two parenthesis.
I just decided to work on the compiled version and it works like a charm. If i don't get the shortcuts, i won't use texmacs ...
So here we go back to the packaging question.
If the problem i encountered are shared by all ubuntu 13.10 users, we won't get a lot of new texmacs users ... since texmacs is known among latex users for his really well thougth shortcuts (which, i assumed, don't work as expected under ubuntu 13.10 official package).