That has been suggested in the past but ascii 0-31 are called non-printable characters, it makes sense fonts do not render them with a visible glyph.
Yet they do, the problem is now that you're unhappy with the glyphs they use (or at least for those two control codes).
And since mIRC lets windows handle the way the characters are displayed in editboxes, it's' more or less a problem depending on the font used. Note how you're not reporting the problem for others control codes because you're fine with how they are rendered.
I agree though, it would be better if control codes were rendered with consistency regardless of the font
