Two suggestions, both associated with ascii art:
- Currently it's not possible to use monospace ascii art in posts and comments because the line-height property is set to 1.6 instead of the default 1. I suggest either to change the default value of the style or even better -- to install the line height plugin for CKEditor, provided that it's compatible with editor.
- It's also not possible to use Shift_JIS art because the required fonts are not in the list of options. My suggestions is to add
font-family: Mona, "MS PGothic";
to the list of fonts.