No reason to investigate, Yiannis. This is not a Code::Blocks problem. I am sure it is not, because I can do the same with other programs on my Computer
In order to have your text aligned smoothly, you should either use the tab char instead of spaces (you can configure the editor and the code formatter plugin to use either (and convert between)), or you should use a fixed pitch font. Sounds obvious. Now you tell me that you are using a fixed pitch font. No, you are not.
The font Ludida Console
is a fixed pitch font just like Courier New. However, Lucida Console, unlike Courier New, does not come with a bold font face. So what happens is that the "smart" font substitution built into Windows chooses the next best font to display bold text, which is Lucida Sans in this case.
Lucida Sans is not fixed pitch, hence the problem.
Another possibility would be to turn off "smart" font substitution, then Windows will use Lucida Console and create a "faux bold" effect (which will still be fixed pitch). I don't remember how you turn that off, though... some occult registry key probably.