I have tried code::blocks 16.01 on ubuntu 16.04.3, ubuntu 17.04, mint 18.2 xfce, and have same problem as below:
Chinese characters displayed in the code editor were mutilated because they were lower than English characters. and I have tried several fonts, no lucky.
Please take a look these screenshots on ubuntu:
Editor settings choose font DejaVu Sans Mono 11
use font ubuntu Mono 11 get even worse