Thunderbird 31.0 and 34.0a1 20140723 on Windows 8.1 64 bit Pretty similar to bug 1003856. When entering an address in the message compose window and starting in the middle of the name and writing until only one suggestions is left, clicking into the textarea for the mail body will leave a combination from typed letters and the autocomplete suggestion in the addressing widget. Example: 1. Have two contacts: a) "Ben Hardwood <mail@example.com>" b) "Claire Hastings <claire.h@example.com>" 2. Type: har 3. Click into the message body. Actual result in the recipient line: har >> Ben Hardwood <mail@example.com> Expected result: Ben Hardwood <mail@example.com>