This problem has been going on for years and still exists today. When making a post or comment, if there are any unsupported special characters in the body of text when posted, all of the text following the first special character will be deleted (including the character itself). Unsupported special characters include such things as "smart quotes" directly generated by the WordPress code, and many others symbols.
Here's another fun fact. If I put in the HTML code for an unsupported special character, posting will work fine. However, if I switch from source view to the rich editor view and back again, it will convert the HTML code to the actual character. Then, posting will delete all the text after it.
Is anybody aware of this? Are there plans to fix this? I've lost many good posts due to this (it's been present since before auto-save was implemented). One of my readers lost a couple comments because of it. It's a shame.