Are you referring to the SourceEditor?
If yes, which version of Lazarus?
And if yes, can you supply:
1) A screenshot
2) a sample text file
Also make sure you have a monospaced font selected.
The option dialog, does allow to choose any font you like, even none-monospaced.
Yet the source editor is designed for monospaced fonts. It does often work with none-monospaced fonts too, but does NOT necessarily that good. (and that has only been tested with latin chars)