An annoyance I have with Opera’s Mail client is that if you highlight some text an in email you are reading, and then reply to the email, only the highlighted text will be quoted. This is obviously a feature that is by-design, but I often highlight text as a read with no intention to quote it.
To get around this feature I’ve created new buttons that deselect highlighted text before creating the reply message.
You can drag and drop these to your Opera toolbar, or the raw commands are:
Deselect all,,,"Reply",Reply & Reply
Deselect all,,,"Reply all",Reply All & Reply all