Hello, I'm the one who posted on stackoverflow.

I'm on Windows 7 Entreprise 64 bits (6.1, version 7601).
Here is my first line when I run python:
"Python 2.7.9 (default, Dec 10 2014, 12:28:03) [MSC v.1500 64 bit (AMD64)] on win32".

I think it's linked to the font and its size.
I tested some combinations:
  1 alphanumeric character, bugs (can only see 3 tabs on the 5)
  2 AN chars, bugs (last tabs almost hidden)
  3 AN chars, works
  1 space and 2 AN chars, bugs
  2 spaces and 2 AN chars, works
  2 spaces and 1 AN char, bugs (the last tab is almost hidden)
  3 spaces and 1 AN char, bugs
  4 spaces and 1 AN char, works
I tried the same with a different font (Courier, 12):
  1 alphanumeric character, bugs (the last tab is hidden)
  2 AN chars, works
  3 AN chars, works
  1 space and 2 AN chars, works
  2 spaces and 2 AN chars, works
  2 spaces and 1 AN char, works
  3 spaces and 1 AN char, works
  4 spaces and 1 AN char, works

The code I added for the font:
cfont = tkFont.Font(family="Courier", size=12)
s = ttk.Style()
s.configure('.', font=cfont)