This is just an improvement by obscurity, not a real improvement. A dedicated CAPTCHA hacker just has to create a mapping table once, and use it in all hacking

This is just an improvement by obscurity, not a real improvement. A dedicated CAPTCHA hacker just has to create a mapping table once, and use it in all hacking attempts. The mapping table would map all unicode "A"-lookalikes to "A", and so on. Also, this improvement breaks when a human user tries to use copy and paste to fill the word "apple" into the field instead of typing it in. Furthermore, aren't most CAPTCHAs broken by humans being paid for that task?