I know this has been pointed out before...
When leaving a comment, look at the captcha code box. Immediately below the "refresh" icon you click to get a new code, there's another icon--a speaker with waves coming out of it, universal for "sound". If you click that, you'll get an audio cue, and you can type in the code based on what you hear. This feature is included specifically for people who have trouble seeing the codes.
Failing that, you can also try enlarging it by using your browser's "zoom" feature, which will appear in a drop-down when you click "view" in the tool bar at the top of the window.
Unfortunately, making the codes "easier to read" defeats their purpose to varying degrees. You'd have a lot more of the type of thing I started this thread for in the first place (BTW, you're welcome, admins

), and worse.